UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS 


COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


THE 

PRINCIPLES  OP  WINE-MAKING 


By  FREDERIC  T.  BIOLETTI. 


BULLETIN  No.  213 

(Berkeley.  Cal.,  May.  1911) 


SACRAMENTO 

W.    W.    SHANNON  -  -  -  SUPERINTENDENT   OF    STATE   PRINTING 

1911 


EXPERIMENT  STATION  STAFF. 


E.  J.  Wickson,  M.A.,  Director  and  Horticulturist. 

E.  W.  Hilgard,  Ph.D.,  LL.D.,  Chemist   (Emeritus). 

W.  A.  Setchell,  Ph.D.,  Botanist. 

Leroy  Anderson,  Ph.D.,  Dairy  Industry  and  Superintendent  University  Farm  Schools. 

M  E.  Jaffa,  M.S.,  Nutrition  Expert,  in  charge  of  the  Poultry  Station. 

R.  H.  Loughridge,  Ph.D.,  Soil  Chemist  and  Physicist  (Emeritus). 

C.  W.  Woodworth,  M.S.,  Entomologist. 

Ralph  E.  Smith,  B.S.,  Plant  Pathologist  and  Superintendent  of  Southern  California 

Pathological  Laboratory  and  Experiment  Station. 
G.  W.   Shaw,  M.A.,  Ph.D.,   Experimental  Agronomist  and  Agricultural  Technologist, 

in  charge  of  Cereal  Stations. 

E.  W.  Major,  B.Agr.,  Animal  Industry,  Farm  Manager,  University  Farm,  Davis. 

F.  T.  Bioletti,  M.S.,  Viticulturist. 

B.  A.  Etcheverry,  B.S.,  Irrigation  Expert. 

George  E.  Colby,  M.S.,  Chemist  (Fruits,  Waters,  and  Insecticides),  in  charge  of 
Chemical  Laboratory. 

H.  J.  Quayle,  A.B.,  Assistant  Entomologist,  Plant  Disease  Laboratory,  Whittier. 

W.  T.  Clarke,  B.S.,  Assistant  Horticulturist  and  Superintendent  of  University  Exten- 
sion in  Agriculture. 

H.  M.  Hall,  Ph.D.,  Assistant  Botanist. 

C.  M.  Haring,  D.V.M.,  Assistant  Veterinarian  and  Bacteriologist. 
John  S.  Burd,  B.S.,  Chemist,  in  charge  of  Fertilizer  Control. 

E.  B.  Babcock,  B.S.,  Assistant  in  Agricultural  Education. 
W.  B.  Herms,  M.A.,  Assistant  Entomologist. 

J.  H.  Norton,  M.S.,  Assistant  Chemist,  in  charge  of  Citrus  Experiment  Station,  River- 
side. 
W.  T.  Horne,  B.S.,  Assistant  Plant  Pathologist. 

J.  E.  Corr,  Ph.D.,  Assistant  Pomologist,   Plant  Disease  Laboratory,  Whittier. 
C.  B.  Lipman,  Ph.D.,  Soil  Chemist  and  Bacteriologist. 
R.  E.  Mansell,  Assistant  in  Horticulture,  in  charge  of  Central  Station  grounds. 

A.  J.  Gaumnitz,  M.S.,  Assistant  in  Cereal  Investigations,  University  Farm,  Davis. 

E.  H.  Hagemann,  Assistant  in  Dairying,  Davis. 

B.  S.  Brown,  B.S.A.,  Assistant  in  Horticulture,  University  Farm,  Davis. 

F.  D.  Hawk,  B.S.A.,  Assistant  in  Animal  Industry. 

J.  I.  Thompson,  B.S.,  Assistant  in  Animal  Industry,  Davis. 

R.  M.  Roberts,  B.S.A.,  University  Farm  Manager,  University  Farm,  Davis. 

J.  C.  Bridwell,  B.S.,  Assistant  Entomologist. 

C.  H.  McCharles,  B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 
N.  D.  Ingham,  B.S.,  Assistant  in  Sylviculture,  Santa  Monica. 

E.  H.  Smith,  M.S.,  Assistant  Plant  Pathologist. 
T.  F.  Hunt,  B.S.,  Assistant  Plant  Pathologist. 

C.   O.   SMirti,  M.S.,   Assistant  Plant  Pathologist,   Plant  Disease  Laboratory,   Whittier. 

F.  L.  Yeaw,  B.S.,  Assistant  Plant  Pathologist,  Vacaville. 
F.  E.  Johnson,  B.L.,  M.S.,  Assistant  in  Soil  Laboratory. 
Charles  Fuchs,  Curator  Entomological  Museum. 

P.  L.  Hibbard,  B.S.,  Assistant  in  Fertilizer  Control  Laboratory. 

L.   M.   Davis,  B.S.,   Assistant  in  Dairy  Husbandry,  University  Farm,   Davis. 

L.  Bonnet,  LA.,  Assistant  in  Viticulture. 

S.  S.  Rogers,  B.S.,  Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

B.  A.  Madson,  B.S.A.,  Assistant  in  Cereal  Laboratory. 

Walter  E.  Packard,  M.S.,  Field  Assistant,  Imperial  Valley  Investigation,  El  Centre 

M.  E.  Stover,  B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 

P.  L.  McCreary,  B.S.,  Laboratory  Assistant  in  Fertilizer  Control. 

F.  Flossfeder,  Assistant  in  Viticulture,  Davis. 

W.  V.  Cruess,  B.S.,  Assistant  in  Zymology. 

E.  E.  Thomas,  B.S.,  Assistant  Chemist,  Plant  Disease  Laboratory,  Whittier. 

Anna  Hamilton,  Assistant  in  Entomology. 

Mrs.  D.  L.  Bunnell,  Secretary  to  Director. 

W.  H.  Volck,  Field  Assistant  in  Entomology,  Watsonville. 

E.  L.  Morris,  B.S.,  Field  Assistant  in  Entomology,  San  Jose. 

J.  S.  Hunter,  Field  Assistant  in  Entomology,  San  Mateo. 

J.  C.  Roper,  Patron,  University  Forestry  Station,  Chico. 

J.  T.  Bearss,  Foreman,  Kearney  Park  Station,   Fresno. 

E.  C.  Miller,  Foreman,  Forestry  Station,  Chico. 


CONTENTS. 


I.     INTRODUCTION.  Page. 

II.     THE  NATURE  OF  WINE •_  396 

a.  Definitions    396 

b.  Standards    396 

c.  Classifications    399 

III.  THE  BIOLOGICAL  THEORY  OF  WINE-MAKING 405 

a.  Causes  of  variation  in  character  and  quality 405 

6.  Outline  of  operations  of  wine-making : 406 

c.  The  relation  of  micro-organisms  to  uine-making 406 

d    Causes   of   fermentation 407 

IV.  MICRO-ORGANISMS  FOUND  ON  GRAPES 408 

a.  Molds:  1.  Blue  Mold;  2.  Black  Mold;  3.  Gray  Mold 408 

b.  Yeasts,    Saccharomyces :  1.  Nutrition ;    2.  Relation    to    oxygen ;    3. 

Relation  to  temperature ;  4.  Relation  to  acids ;  5.  Relation  to 
sulfurous  acid  ;  6.  Morphology  of  wine  yeasts ~ 411-415 

c.  Pseudo-yeasts    415 

d.  Bacteria    .. 417 

V.     MICRO-ORGANISMS  FOUND  IN  WINE 417 

a.  Aerobic    organisms:  1.  Mycodermae ;    2.  Acetic    bacteria 417,418 

b.  Anaerobic  organisms:  1.   Slime  forming  bacteria;   2.  Propionic  and 

lactic  acid  bacteria ;  3.  Mannitic  bacteria ;  4.  Butyric  acid  bac- 
teria     _419,  420 

VI.     CONTROL  OF  THE  MICRO-ORGANISMS 421 

a.  Before   fermentation:  1.  Gathering   the    Grapes;    2.  Transportation 

of  Grapes ;  3.  Cleanliness ;  4.  Defecation  of  Must ;  5.  Steriliza- 
tion;   6.  Starters;    7.  Pure   Yeast 421-427 

b.  During    Fermentation:  1.   Starting    temperature;    2.  Crushing:    3. 

Aeration ;  4.  Use  of  sulfurous  acid ;  5.  Increase  of  acidity ;  6. 
Modification  of  sugar  contents  ;  7.  Temperature  of  fermentation  : 
8.  Aeration   during   fermentation 427-434 

c.  After   Fermentation:  1.  Aging;    2.  Racking;    3.  Exclusion    of    air; 

4.   Sulfuring ;    5.  Cellar    hygiene ;    6.  Clarification ;    7.  Filtration : 

8.  Heating;  9.  Pasteurization;   10.  Cooling;   11.  Bottling 434-442 


THE  PRINCIPLES  OE  WINE-MAKING. 


I.    INTRODUCTION. 

The  Legislature  of  the  State  of  California  in  1909  passed  an  act  to 
provide  for  experiment  and  research  work  in  viticulture,  to  be  prosecuted 
by  the  Regents  of  the  University  of  California,  and  made  an  appropria- 
tion therefor.  This  act  specified  a  number  of  lines  of  work  which  were 
to  be  undertaken,  including  all  the  more  important  branches  of  grape- 
growing  and  wine-making.  It  also  directed  that  reports  should  be  made 
on  "all  matters  appertaining  to  the  viticultural  industry  pertinent  to 
the  successful  conduct  of  the  business  that  may  be  of  general  public 
interest,  use  and  profit." 

In  accordance  with  the  provisions  of  this  act  the  Viticultural  Division 
of  the  College  of  Agriculture  has  undertaken  research  and  experimental 
work  in  those  directions  which  seemed  of  most  pressing  importance,  and 
for  which  the  resources  of  the  division  were  most  available. 

The  principal  lines  of  work  undertaken  have  been:  (1)  the  search 
for  the  best  resistant  stocks  for  various  localities  differing  in  climate 
and  soil, — and  for  various  varieties  of  wine,  raisin  and  table  grapes; 

(2)  the   introduction   and   testing   of  new   and   promising   varieties; 

(3)  investigation  of  the  nature  and  control  of  various  insect  pests  and 
diseases  of  the  vine;  (4)  tests  of  improved  methods  of  grafting  and 
establishing  vineyards;  (5)  trials  of  methods  of  fertilization  of  vine- 
yards; (6)  investigation  of  improved  methods  of  fermentation  and 
handling  of  wine,  and  of  the  utilization  of  the  by-products  of  the  vine- 
yard and  cellar. 

The  present  bulletin  is  published  in  accordance  with  the  special  pro- 
vision of  the  act  which  requires  the  Regents  of  the  University  of  Cali- 
fornia to  ' '  ascertain  #  *  *  the  most  important  methods  of  vinifica- 
tion  ***'»,  As  the  profit  of  the  vineyards  of  the  State  depends 
upon  the  successful  marketing  of  the  finished  product,  it  is  essential 
that  the  product  be  handled  properly  and  in  accordance  with  modern 
and  scientific  methods.  As  the  larger  part  of  the  product  of  our  vine- 
yards is  used  in  the  manufacture  of  wine,  it  is  very  necessary  that  this 
wine  should  be  properly  made. 

In  the  general  effort  of  farmers,  especially  of  fruit  growers,  to  stand- 
ardize and  improve  the  quality  of  their  products,  the  wine-makers  are 
not  conspicuous.  Some  of  our  wine  is  good,  some  of  it  very  good,  but 
much  of  it  is  indifferent,  and  too  large  a  portion,  frankly  bad. 

There  is  no  reason,  except  lack  of  skillful  wine-making,  why  any  Cali- 
fornian  wine  should  be  bad.  While  some  improvement  might  be  made  in 
our  grapes  in  many  cases,  by  a  better  choice  of  varieties,  there  is  proba- 


396  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

bly  no  grape-growing  country  where  the  grapes  as  a  whole  are  more  gen- 
erally suitable  for  making  good,  sound  wine.  They  are  seldom  injured 
by  diseases  or  inclement  weather  and  their  commonest  fault,  that  of 
excess  of  sugar,  is  the  most  easily  avoided  and  remedied.  The  com- 
parative regularity  of  our  crops  and  the  constancy  of  their  quality 
give  us  advantages  which  are  counteracted  to  a  great  extent  by  the  back- 
ward methods  of  many  of  our  wine-makers.  "Whatever  other  reasons 
there  may  be  for  the  present  prejudice  against  Californian  wines,  the 
fact  that  we  produce  so  much  unnecessarily  inferior  wine  is  quite  suffi- 
cient, to  account  for  it.  Though  equally  inferior  wine  is  produced  in 
all  other  wine-making  countries,  most  of  it  is  consumed  in  the  country 
itself.  Much  of  our  poorest  wine  is  sent  out  of  the  State  and  does 
serious  injustice  to  our  good  wines.  All  our  wine  ought  to  be  good, 
and  it  depends  principally  on  the  wine-makers  to  make  it  so. 


II.    THE  NATURE  OF  WINE. 

(a)  Definitions. — Many  attempts  have  been  made  by  authors  and 
legislators  to  give  a  clear  definition  of  wine.  They  practically  all  agree 
that:  ''wine  is  the  product  of  the  alcoholic  fermentation  of  the  grape." 
This  excludes  all  liquids  or  beverages  made  from  other  fruits  or  sub- 
stances. This  is  in  accord  with  the  derivation  of  the  word  and  the 
practice  of  centuries.  Wine,  therefore,  can  only  be  made  from  grapes 
and  must  contain  alcohol  produced  by  fermentation. 

Most  definitions  contain  also  the  proviso  that  wine  must  be  made  by 
the  usual  cellar  treatment.  When  the  attempt  is  made  to  state  exactly 
what  the  ' '  usual  cellar  treatment ' '  is,  the  definitions  vary  considerably. 
They  all  agree  in  this,  however,  that  they  seek  to  confine  the  operations 
of  the  wine-maker  to  those  practices  which  secular  experience  has  shown 
to  be  necessary  for  the  production  of  a  stable,  healthful  and  agreeable 
beverage.  To  do  this,  they  limit  all  additions  to  the  grapes  or  wine  to 
those  substances  which  occur  naturally  in  sound,  ripe  grapes  or  which 
long  experience  has  shown  to  be  necessary  to  the  preservation  of  the 
desirable  qualities  of  wine  without  adding  any  qualities  which  are 
undesirable.  The  mechanical  operations  are  usually  left  to  the  choice 
of  the  manufacturer.  The  addition  of  even  harmless  or  useful  sub- 
stances, however,  is  allowed  only  within  prescribed  limits.  These  limits 
vary  with  different  laws  and  definitions.  The  effort  is  usually  made  to 
place  them  where  they  render  possible  all  additions  which  will  result  in 
an  amelioration  or  bettering  of  the  wine  and  will  not  defraud  or  deceive 
the  buyer. 

(b)  Standards. — As  grapes  of  various  localities,  varieties  and  seasons 
vary  very  much  in  (composition,  an  addition  that  in  one  case  would  be 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  397 

desirable  would  do  harm  in  another ;  an  addition  that  in  one  case  would 
provide  the  consumer  with  a  more  agreeable,  healthful  and  valuable 
beverage  would  in  another  simply  supply  him  with  a  substitute  or 
inferior  product.  The  central  idea  of  all  additions  must  be  that  they 
are  intended  to  improve  the  product  and  not  to  defraud  the  buyer. 
This  is  the  distinction  to  be  drawn  between  amelioration  and  sophis- 
tication. 

Some  concrete  illustrations  may  make  this  clearer.  If  the  wine- 
maker  attempts  to  ferment  very  ripe  grapes  containing  over  25  per  cent 
of  sugar,  the  result  will  often  be  that  the  fermentation  will  be  incomplete 
and  the  resulting  wine  inferior  or  spoiled.  By  adding  a  carefully  cal- 
culated amount  of  water  to  the  crushed  grapes  he  can  so  reduce  the 
sugar  contents  as  to  insure  a  complete  fermentation  and  a  sound,  good 
wine.  While  this  increases  the  volume  of  wine  made,  slightly',  it  is  as 
much  to  the  benefit  of  the  consumer  as  to  that  of  the  manufacturer  as 
he  is  supplied  with  a  better  product.  If  the  dilution  is  accurately 
done,  the  resulting  wine  will  contain  all  the  ingredients  of  a  good  wine 
in  just  proportions  and  the  consumer  is  in  no  way  defrauded.  This 
dilution  would  be  proper  amelioration  of  the  wine. 

On  the  other  hand,  an  equal  addition  of  water  to  under-ripe  grapes 
might  result  in  a  wine  deficient  in  alcohol  and  body  and  of  inferior 
quality,  and  the  only  object  of  such  dilution  would  be  an  increase  of 
volume.  In  this  case,  the  buyer  would  be  defrauded.  By  adding  to 
such  grapes  both  water  and  sugar  the  alcoholic  contents  of  the  wine 
could  be  kept  normal,  but  all  the  other  ingredients  would  be  deficient 
and  the  practice  become  mere  "stretching."  Such  additions  would 
constitute  sophistication. 

Owing  to  the  varying  composition  of  good  grapes,  it  is  difficult  to  fix, 
exactly,  just  proportions  for  all  additions.  Maxima  limits  may  be 
assigned,  on  the  theory  that  grapes  which  require  additions  exceeding 
these  limits  are  totally  unfitted  for  wine-making.  The  difficulty  is 
resolved  usually  by  fixing  such  maxima  and  also  certain  standards  of 
composition  for  the  wine.  So  long  as  these  maxima  are  not  exceeded 
and  the  finished  wine  possesses  the  various  ingredients  within  assigned 
limits  of  quantity,  the  additions  are  considered  legitimate.  The  stand- 
ards usually  take  into  consideration  not  only  the  absolute  amounts  of 
each  ingredient  but  their  relative  proportions.  It  has  been  found  that 
in  wines  made  from  suitable  grapes  there  exist  always  certain  har- 
monious ratios  between  the  alcohol  and  the  extract  and  between  the 
alcohol  and  the  acidity.  An  addition  which  does  not  destroy  these  ratios 
is  allowable.  In  a  few  cases,  wines  made  from  grapes  without  additions 
of  any  kind  will  fall  outside  of  these  ratios.  This  simply  proves  that 
the  grapes  were  unsuitable  for  wine-making,  and  the  wine  might  have 


398  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

been  improved  by  additions  which  would  have  brought  about  the  estab- 
lished ratios. 

Various  standards  of  composition  have  been  promulgated  by  various 
governments,  but  most  of  them  are  based  on  those  of  France.  The 
United  States  "Standards  of  Purity  for  Food  Products"  defines  wine 
as  follows : 

1.  *Wine  is  the  product  made  by  the  normal  alcoholic  fermentation  of  the  juice 
of  sound,  ripe  grapes  and  the  usual  cellar  treatment,  (a)  and  contains  not  less  than 
seven  nor  more  than  sixteen  per  cent  of  alcohol,  by  volume,  and,  in  one  hundred 
cubic  centimeters  (20°C),  not  more  than  one  tenth  gram  of  sodium  chlorid  nor 
more  than  two  tenths  gram  of  potassium  sulphate ;  and  for  red  wine  not  more  than 
fourteen  hundredths  gram,  and  for  white  wine  not  more  than  twelve  hundredths 
gram  of  volatile  acids  produced  by  fermentation  and  calculated  as  acetic  acid. 
Red  ivine  is  wine  containing  the  red  coloring  matter  of  the  skins  of  grapes.  White 
wine  is  wine  made  from  white  grapes  or  the  expressed  fresh  juice  of  other  grapes. 

2.  Dry  wine  is  wine  in  which  the  fermentation  of  the  sugars  is  practically  com- 
plete and  which  contains,  in  one  hundred  cubic  centimeters  (20°C.)  less  than  one 
gram  of  sugars,  and  for  dry  red  wine  not  less  than  sixteen  hundredths  gram  of  grape 
ash  and  not  less  than  one  and  six  tenths  grams  of  sugar-free  grape  solids,  and  for  dry 
white  wine  not  less  than  thirteen  hundredths  gram  of  grape  ash  and  not  less  than  one 
and  four  tenths  grams  of  sugar-free  grape  solids. 

3.  Fortified  dry  wine  is  dry  wine  to  which  brandy  has  been  added  but  which 
conforms  in  all  other  particulars  to  the  standard  of  dry  wine. 

4.  Sweet  ivine  is  wine  in  which  the  alcoholic  fermentation  has  been  arrested,  and 
which  contains,  in  one  hundred  cubic  centimeters  (20°C. )  not  less  than  one  gram  of 
sugars,  "and  for  sweet  red  wine  not  less  than  sixteen  hundredths  gram  of  grape  ash, 
and  for  sweet  white  wine  not  less  than  thirteen  hundredths  gram  of  grape  ash. 

5.  Fortified  sweet  wine  is  sweet  wine  to  which  wine  spirits  have  been  added. 
By  act  of  Congress,  "sweet  wine"  used  for  making  fortified  sweet  wine  and  "wine 
spirits,"  used  for  such  fortification  are  defined  as  follows  (section  43,  act  of  October 
1,  1890,  26  Stat.  567,  as  amended  by  section  68,  act  of  August  27,  1894,  28  Stat.  509, 
and  further  amended  by  act  of  Congress  approved  June  7,  1906)  :  "That  the  wine 
spirits  mentioned  in  section  42  of  this  act  is  the  product  resulting  from  the  distilla- 
tion of  fermented  grape  juice  to  which  water  may  have  been  added  prior  to,  during, 
or  after  fermentation,  for  the  sole  purpose  of  facilitating  the  fermentation  and 
economical  distillation  thereof,  and  shall  be  held  to  include  the  products  from  grapes 
or  their  residues  commonly  known  as  grape  brandy  ;  and  the  pure  sweet  wine,  which 
may  be  fortified  free  of  tax,  as  provided  in  said  section,  is  fermented  grape  juice 
only,  and  shall  contain  no  other  substance  whatever  introduced  before,  at  the  time 
of,  or  after  fermentation,  except  as  herein  expressly  provided  ;  and  such  sweet  wine 
shall  contain  not  less  than  four  per  centum  of  saccharine  matter,  which  saccharine 
strength  may  be  determined  by  testing  with  Balling's  saccharometer  or  must  scale, 
such  sweet  wine,  after  the  evaporation  of  the  spirits  contained  therein,  and  restoring 
the  sample  tested  to  original  volume  by  addition  of  water ;  provided,  that  the  addition 
of  pure  boiled  or  condensed  grape  must  or  pure  crystallized  cane  or  beet  sugar  or 
pure  anhydrous  sugar  to  the  pure  grape  juice  aforesaid,  or  the  fermented  product 
of  such  grape  juice  prior  to  the  fortification  provided  by  this  act  for  the  sole 
purpose  of  perfecting  sweet  wine  according  to  commercial  standard,  or  the  addition 
of  water  in  such  quantities  only  as  may  be  necessary  in  the  mechanical  operation  of 
grape    conveyors,    crushers,    and    pipes    leading    to    fermenting    tanks,    shall    not   be 

*  "Standards  or    Purity   for    Food    Products"    Circular   No.    19,   Office   of   Secretary, 
U.  S.    Department  of  Agriculture!   Washington,    l  >.   C.      (a)   The  subject  of  sulphurous 
acid  in   wine  Is  reserved   for  consideration   In  connection  with  the  schedule  "Preserv- 
and  <  iolorlng  Matters." 


Bulletin  213]  THe  PRINCIPLES  OF  WINE-MAKING.  399 

excluded  by  the  definition  of  pure  sweet  wine  aforesaid  :  provided,  howevi  /.  that  the 
cane  or  beet  sugar,  or  pure  anhydrous  sugar,  or  water,  so  used  shall  not  in  either 
case  be  in  excess  of  ten  per  centum  of  the  weight  of  the  wine  to  be  fortified  tinder 
this  act;  and  provided,  farther,  that  the  addition  of  water  herein  authorized  shall 
be  under  such  regulations  and  limitations  as  the  Commissioner  of  Internal  Revenue, 
with  the  approval  of  the  Secretary  of  the  Treasury,  may  from  time  to  time  prescribe  ; 
but  in  no  case  shall  such  wines  to  which  water  has  been  added  be  eligible  for  fortifica- 
tion under  the  provisions  of  this  act  where  the  same,  after  fermentation  and  before 
fortification,  have  an  alcoholic  strength  of  less  than  five  per  centum  of  their  volume.'' 

6.  Sparkling  icine  is  wine  in  which  the  after  part  of  the  fermentation  is  completed 
in  the  bottle,  the  sediment  being  disgorged  and  its  place  supplied  by  wine  or  sugar 
liquor,  and  which  contains,  in  one  hundred  cubic  centimeters  (20°C. ),  not  less  than 
twelve  hundredths  gram  of  grape  ash. 

7.  Modified  wine,  ameliorated  wine,  corrected  wine,  is  the  product  made  by  the 
alcoholic  fermentation  with  the  usual  cellar  treatment,  of  a  mixture  of  the  juice  of 
sound,  ripe  grapes  with  sugar  (sucrose),  or  a  sirup  containing  not  less  than  sixty-five 
per  cent  of  sugar  (sucrose)  and  in  quantity  not  more  than  enough  to  raise  the 
alcoholic  strength  after  fermentation  to  eleven  per  cent  by  volume. 

8.  Raisin  icine  is  the  product  made  by  the  alcoholic  fermentation  of  an  infusion 
of  dried  or  evaporated  grapes,  or  of  a  mixture  of  such  infusion  or  of  raisins  with 
grape  juice. 

A  wine  to  be  legal  must  not  only  satisfy  the  requirements  of  these 
standards  but  must  conform  to  certain  other  regulations  of  pure  food 
laws — federal  and  state.  These  include  the  prohibition  of  all  substances 
which  are  poisonous  or  commonly  regarded  as  injurious  to  health.  An 
exception  is  made  of  certain  antiseptics  such  as  benzoic  acid  which  may 
be  used  within  specified  limits  if  the  fact  of  their  presence  is  stated 
plainly  on  the  containing  vessel. 

The  use  of  certain  substances  such  as  tannin  and  albumen,  which 
have  been  used  for  time  immemorial  in  the  treatment  of  wine,  is 
allowed.  Such  substances  are  used  only  in  minute  quantities  and  solely 
for  the  purpose  of  improving  the  product  and  there  can  be  no  object 
for  the  manufacturer  to  use  them  unnecessarily  or  in  undue  quantities. 
The  same  can  be  said  of  the  use  of  citric,  tartaric,  and  sulfurous  acids. 
Such  substances  are  used  only  to  increase  the  quality  and  the  Avhole- 
someness  of  the  wine,  and  in  no  way  to  disguise  inferior  material  or 
careless  manipulation  as  is  the  case  with  salicylic  acid,  benzoates  and 
similar  preservatives. 

(c)  Classifications. — A  certain  differentiation  into  classes  is  made 
by  the  above  standards.  These  classes  are  based  partly  on  the  nature 
of  the  raw  material,  partly  on  the  composition  of  the  wine  and  partly 
on  the  methods  of  manufacture. 

A  very  much  more  detailed  and  complicated  classification  is  neces- 
sary for  commercial  uses.  Wine  contains  not  only  the  half  dozen  sub- 
stances usually  determined  in  an  ordinary  analysis,  but  more  or  less  of 
a  very  large  number  of  others  which  have  a  very  appreciable  effect  on 
the  character  and  quality  of  the  wine.     The  number  of  substances  and 


400  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 

compounds  which  have  been  found  in  pure  wine,  are  reckoned  by  hun- 
dreds. Many  of  these,  which  are  in  amounts  so  small  as  to  be  undeter- 
minable quantitatively,  may  influence  the  quality  of  the  wine  notably. 

Many  attempts  have  been  made  to  devise  a  rational  classification  of 
the  large  number  of  variations  brought  about  by  this  complex  and 
variable  composition.  Most  of  them  include  scores  of  types  and  hun- 
dreds of  varieties.  While  such  classifications  correspond  to  actual  and 
appreciable  differences,  they  are  unnecessary  to  the  wine-maker,  and 
a  much  simpler  classification  will  serve  his  purpose. 

Commencing  with  the  assumption  that  all  wines  are  made  from 
grapes,  they  may  be  divided  into  a  few  great  classes  depending  on  the 
way  these  grapes  are  handled,  i.  e.,  the  methods  of  manufacture.  These 
variations  in  the  methods  of  manufacture  will  correspond  to  certain 
easily  defined  differences  in  composition  and  character.  We  are  thus 
enabled  to  segregate  all  wines  into  three  groups,  each  with  two  similar 
divisions : 

TABLE  I. 

1.  Dry  wines  (a)  red;  (6)  white. 

2.  Sweet  wines  (a)  red;  (5)  white. 

3.  Sparkling  wines  (a)  red;   (5)  white. 

To  these  may  be  added  to  conform  with  the  official  classification  and 
commercial  practice : 

4.  Modified  wine  (a)  red;   (6)  white. 

5.  Raisin  wine  (a)  red;   (6)  white. 

6.  Carbonated  wine  (a)  red;  (b)  white. 

Groups  four,  five  and  six,  however,  can  hardly  be  considered  as 
natural  wines  either  in  origin  or  character  and  will  not  be  considered 
here. 

A  dry  wine  is  one  in  which,  by  fermentation,  all  sugar  perceptible 
to  the  taste  has  been  eliminated.  A  sweet  wine  is  one  in  which  suffi- 
cient sugar  remains  after  fermentation  to  give  a  noticeable  sweet  taste 
The  two  groups  are  on  the  whole  perfectly  distinct  and  the  main  cause 
of  the  distinction  is  that  in  the  former  every  effort  is  made  by  the  wine- 
maker  to  carry  on  the  fermentation  continuously  until  all  the  sugar  has 
been  broken  up  into  alcohol  and  carbonic  acid,  and,  in  the  latter,  fer- 
mentation is  stopped  intentionally  by  the  addition  of  alcohol  while  a 
certain  amount  of  unchanged  sugar  remains.  This  addition  is  called 
fortification.  Very  few  wines  are  absolutely  dry  in  the  sense  that  all 
the  sugar  has  disappeared.  In  young  wines  there  will  nearly  always 
remain  several  hundredths  of  one  per  cent.  A  few  wines  classed  as  dry, 
such  as  certain  Sauternes  and  some  Rhine  wines  may  contain  several 
tenths  of  one  per  cent.  Such  wines  are  difficult  to  handle  and  easily 
subject  to  injurious  changes  but  are  often  among  the  most  prized  and 
valuable. 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKIXG.  401 

Sweet  wines  vary  very  much  in  the  amount  of  sugar  they  contain, 
which  may  range  from  two  or  three  per  cent  to  ten  per  cent  or  more. 
The  amount  is  determined  in  some  cases  by  the  stage  of  fermentation 
at  which  the  alcohol  is  added  and  in  others  by  the  addition  of  must  or 
grape  syrup  after  fortification.  A  few  wines  in  this  class  are  made 
without  fortification  by  the  use  of  very  sweet  grapes.  Such  wines  are 
difficult  to  make  and  are  produced  only  locally. 

There  are  differences  besides  those  of  sweetness  which  distinguish 
most  dry  wines  from  most  sweet  wines.  The  chief  of  these  is  the  rancio, 
sherry  or  madeira  taste,  which  is  characteristic  of  most  sweet  wines,  and 
is  due  to  rapid  and  ample  oxidation.  This  taste  may  occur  in  dry  wines, 
but  is  there  considered  a  defect  except  in  a  few  wines  such  as  dry  sherry 
which  are  usually  classed  with  the  sweet.  The  methods  of  making  sweet 
wines  are  very  diverse  and  are  not  treated  in  this  bulletin.  In  the 
United  States  they  must  be  made  under  certain  regulations  of  the 
Internal  Revenue  Department. 

A  sparkling  wine  contains  sufficient  dissolved  carbonic  acid  gas  to 
cause  a  pressure  of  five  to  six  atmospheres  in  the  bottle  at  a  temperature 
of  50°  F.  The  wine  is  made  by  practically  the  same  processes  as  dry 
wine  and  the  sparkling  quality  given  later  by  supplementary  fermenta- 
tion in  the  bottle. 

The  manufacture  of  sparkling  wines  requires  special  skill,  knowledge, 
and  equipment  and  is  not  within  the  province  of  the  ordinary  wine- 
maker. 

All  the  above  classes  of  wine  may  be  red  or  white  depending  upon 
whether  the  color. is  extracted  from  the  skins  or  not.  While  the  pres- 
ence or  absence  of  red  coloring  matter  is  the  most  obvious  difference 
between  these  two  classes,  certain  other  differences  of  composition  are 
equally  important.  A  red  wine  contains  tannin  and  more  extract  than 
a  white  wine.  The  color,  tannin  and  higher  extract  are  due  to  the 
fermentation  of  the  must  in  the  presence  of  the  skins  or  sometimes  to 
the  heating  of  the  must  and  skins  together  before  fermentation.  A 
wine  made  from  white  grapes  by  these  methods  would  have  all  the 
qualities  of  a  red  wine,  except  the  color.  Such  a  wine  would  fit  into 
no  classification  and  would  be  almost  unmarketable.  On  the  other  hand, 
a  wine  could  be  made  from  grapes  with  red  juice  or  by  partial  extraction 
of  the  skins,  which,  except  for  its  light  red  or  rose  color,  would  have 
all  the  qualities  of  a  white  wine.  A  certain  quantity  of  this  last  varia- 
tion is  made  in  some  localities  and  is  known  by  various  names  such  as 
vin  rose,  schiller  wein,  vino  siciliano.  Such  wines  are  made  only  in 
small  quantities  for  special  markets. 

Each  of  the  great  groups  mentioned  above  includes  a  very  large  num- 
ber of  varieties  which  it  is  difficult  to  arrange  logically.    Among  dry  red 


402  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

wines,  for  example,  we  find  in  commerce,  Burgundy,  Medoc,  Hermitage, 
Chianti,  and  numerous  others.  Burgundy  wines  are  further  divided 
into  Chambertin,  Clos  Vougeot,  etc. ;  Medoc  wines  into  Chateau  Latour, 
St.  Estephe,  etc.  Commerce  thus  recognizes  innumerable  variations. 
Most  of  these  variations  are  distinguished  by  the  name  of  a  region,  a 
locality,  or  a  particular  vineyard.  The  wines  of  a  certain  vineyard  are 
further  classified  according  to  the  year  of  the  vintage.  The  brands 
and  names  recognized  in  commerce  are  to  be  reckoned  by  thousands. 

Most  of  these  names  correspond  to  real  differences.  Names  taken 
from  regions,  such  as  Rhine  wines  and  Sauternes,  represent  large  differ- 
ences in  character  easily  distinguishable  by  taste  and  usually  by  chem- 
ical analysis.  Names  representing  vineyards  or  vintage  years  represent 
differences  of  quality,  which  may  be  equally  marked  to  the  practiced 
taster,  but  may  be  difficult  to  indicate  by  chemical  means. 

Names  drawn  from  particular  vineyards  are  properly  considered 
proprietary  and  should  not  be  used,  nor  the  wines  imitated  elsewhere. 
Names  drawn  from  localities  or  regions  are  of  the  same  nature.  They 
represent  qualities  due  to  combinations  of  soil,  climate,  variety,  and 
methods  which  can  not  be  exactly  duplicated  in  any  other  place.  An 
exception  should  probably  be  made  of  certain  names  which,  while 
originally  derived  from  particular  localities  have  come  to  represent, 
through  long  usage,  characters  due  principally  to  methods  of  manu- 
facture.    Such  names  are  Port,  Sherry  and  Champagne. 

The  name  Burgundy  should  be  given  only  to  wine  made  in  Burgundy 
from  Pinot  grapes ;  the  name  Medoc  only  to  wine  made  in  Medoc  from 
Cabernet,  and  the  three  or  four  other  varieties  recognized  there  as 
capable  of  producing  the  wine  to  which  the  region  owes  its  reputation. 

There  seems  to  be  no  sufficient  reason,  however,  why  we  should  not  call 
a  wine  Port  if  it  is  made  of  suitable  grapes  in  the  recognized  way  and 
resembles  those  wines  of  the  banks  of  the  Douro,  which  first  received  this 
name.  "Port,"  is  no  longer  synonymous  with  "wine  of  Oporto." 
All  the  wines  made  in  the  region  of  Oporto  are  not  port,  and  all  port 
docs  not  come  from  that  region. 

With  these  possible  exceptions,  locality  names  should  be  given  only 
to  the  wines  produced  in  the  locality.  This  is  not  only  fair  to  the  con- 
sumer, but  good  policy  in  the  selfish  interest  of  the  producer.  Wines 
are  produced  mosl  profitably  by  those  localities  which  have  an  estab- 
lished reputation.  They  have  a  sure  market  whatever  the  abundance 
ot  crops  in  other  localities.  It  should  be  the  aim  of  each  locality  to 
obtain  and  maintain  a  reputation  that  will  make  them  independent  of 
genera]  competition.  This  can  be  done  only  by  marketing  constantly 
good  wines  under  the  name  of  the  locality. 

A   classification    founded   on   chemical    analysis,   giving  the  general 


Bulletin  218] 


THE    PRINCIPLES    OF    WINE-MAKING. 


403 


character  of  wines,  is  useful  to  the  producer  and  especially  to  the  wine- 
blender.  It  enables  them  to  produce,  buy  and  blend  wines  intelligently, 
to  obtain  a  desired  result. 

From  this  point  of  view,  dry  wines  can  be  segregated  into  three 
groups :  heavy,  medium,  and  light.  The  first  are  produced  from  grapes 
of  high  sugar  contents  and  in  the  warmer  localities,  the  last  from  the 
more  watery  grapes  and  especially  in  the  cooler  localities.  The  sweeter 
grapes  give  wines  with  higher  alcohol  and  extract  and  with  lower  acidity. 
The  following  table  gives  the  usual  range  in  these  three  components : 

TABLE  2. 
Classification   of  Dry   Wines   by   Chemical  Analysis. 


Composition. 

Class. 

Alcohol, 
by  volume. 

Extract. 

Acidity. 
as  tartaric. 

Heavy                  ______ 

13-15 

10-12 

8-  9 

3.0-4.0 
2.0-3.0 
1.5-2.0 

.3-.6 

Medium _  -- 

.6-.8 

Light                                      _  _      -_  _  — -        --  - 

J-.9 

The  alcohol  and  acid  in  natural  wines  vary  in  an  inverse  ratio,  in  such 
a  way  that  the  volume  percentage  of  alcohol  added  to  the  grams  per  liter 
of  acid  as  sulfuric  make  a  sum  lying  between  13  and  17.  This  is  what 
is  known  as  the  acid:  alcohol  ratio,  and  is  used  for  the  detection  of 
watering.  Water  can  be  added  only  to  very  sweet  grapes  without 
exceeding  the  limits  of  this  ratio  and  then  only  in  very  limited 
quantities. 

The  alcohol  and  extract  vary  directly  and  in  such  proportions  that  the 
number  representing  the  extract  in  grams  per  hundred  c.c.  multiplied 
by  the  factor  4.5  gives  a  figure  equal  to  or  greater  than  the  alcohol  in 
grams  per  100  c.c.  With  white  wines,  in  which  the  extract  is  normally 
lower,  the  factor,  6.5  is  used  in  the  same  way.  This  is  known  as  the 
alcohol:  extract  ratio  and  is  used  for  the  detection  of  the  addition  of 
alcohol  to  dry  wines. 

Light  and  heavy  wines  will  vary  also  in  the  amounts  of  tannin  and 
coloring  matter  they  contain,  but  these  have  no  constant  relation  with 
the  other  ingredients.  They  depend  principally  upon  the  variety  of 
grape. 

Each  of  these  groups  can  be  again  subdivided  into  three  other  groups : 
fine,  ordinary,  and  blending  wines.  A  fine  wine  is  one  in  which  all  the 
components  are  in  proper  and  harmonious  proportions  and  which  has 
sufficient  quality  to  be  worth  aging  and  bottling.  These  constitute  in 
most  regions  only  a  small  part  of  the  output.  They  are,  however,  the 
ideal   towards   which   the   efforts   of   every   wine-maker   should   tend 


404 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 


Ordinary  wines  are  those  which  are  sufficiently  harmonious  in  their 
composition  for  direct  consumption,  but  which  exhibit  no  delicacy  of 
flavor  or  bouquet,  and  are  intended  for  bulk  shipments  and  cheap 
markets.  Blending  wines  are  of  various  degrees  of  quality  and  char- 
acter, but  agree  in  showing  a  deficiency  or  excess  of  some  one  or  more 
essential  components.  There  are  blending  wines  with  an  excess  of 
alcohol  or  extract  or  of  color  which  make  them  unsuitable  for  direct 
consumption.  They  serve,  however,  by  blending  to  correct  other  wines 
which  are  deficient  in  these  components.  Where  the  wine  handlers 
have  perfected  their  business,  the  bulk  of  wines  are  used  for  blending, 
for  it  is  only  the  exceptional  wines  which  can  not  be  improved  by  addi- 
tions which  will  correct  their  deficiencies  and  faults. 

If,  together  with  the  chemical  analysis,  we  make  three  grades  based 
on  organoleptic  qualities,  we  have  nine  classes  of  red  and  nine  classes 
of  white  dry  wines. 

TABLE  3. 

General  Classes  of  Dry  Wines. 


Classes. 

Examples. 

1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 

(Red  and  white)  heavy,  fine. 
(Red  and  white)  heavy,  ordinary. 
(Red  and  white)  heavy,  blending. 
(Red  and  white)  medium,  fine. 
(Red  and  white)  medium,  ordinary. 
(Red  and  white)  medium,  blending. 
(Red  and  white)  light,  fine. 
(Red  and  white)  light,  ordinary. 
(Red  and  white)  light,  blending. 

Hermitages,  Hauts  Sauternes. 
Common  wines  of  hot  regions. 
Certain  wines  of  Algeria. 
Fine  Medocs  and  Burgundies. 
Blends  of  classes  3  and  9. 
Common  wines  of  many  regions. 
Best  Moselle  wines. 
Common  Rhenish  wines. 
Common  wines  of  the  Midi. 

This  classification  does  not  take  into  consideration  the  various  faults 
which  wines  may  have  owing  to  defective  methods  of  wine-making. 
They  represent  differences  due  to  variations  in  the  raw  material  which 
exist,  however  perfect  the  processes  of  manufacture. 

In  order  to  obtain  the  best  results  from  a  given  raw  material  the 
principles  of  wine-making  must  be  known  and  applied.  Only  in  this 
way  can  our  wines  be  improved  and  gradually  brought  up  to  the  high 
standard  which  the  general  excellence  of  our  grapes  makes  possible. 

The  conditions  of  the  various  grape-growing  regions  of  California 
are  so  varied  that  we  can  make  wines  conforming  to  all  the  classes  of 
Table  III  with  perhaps  the  exception  of  class  7. 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKING.  405 

III.    THE  BIOLOGICAL  THEORY  OF  WINE-MAKING. 

It  is  now  many  years  since  Pasteur  first  proved  conclusively  that 
alcoholic  fermentation  was  a  vital  phenomenon;  that  it  was  possible 
only  through  the  activities  of  certain  microscopic  living  plants.  This 
discovery  and  the  investigations  that  have  followed  it  have  revolution- 
ized all  the  fermentative  industries.  Wine-making  is  among  the  last 
to  profit  by  this  knowledge.  There  is,  however,  probably  no  other 
industry  which  depends  so  much  for  success  and  failure  at  every  stage 
upon  the  activities  of  micro-organisms. 

(a)  Causes  of  variation  in  character  and  quality. — The  quality  of 
wine  depends  on  two  factors:  (1)  the  nature  of  the  raw  material,  and 
(2)  the  character  of  the  processes  of  manufacture. 

The  nature  of  the  raw  material — the  grape — establishes  certain  limits 
in  the  character  of  the  wine.  We  can  not  make  Sauternes  from  Muscat 
or  Concord,  port  from  Burger,  or  hock  from  Cabernet.  Within  these 
limits,  however,  the  processes  of  manufacture  are  capable  of  influencing 
to  a  very  considerable  extent  the  finished  product. 

How  much  of  the  good  or  bad  quality  of  the  wine  depends  on  each 
factor  it  is  impossible  to  determine  exactly.  Formerly  the  first  factor 
was  accredited  with  almost  the  whole.  With  the  progress  of  investiga- 
tion and  improved  practice,  the  second  factor  is  found  to  exercise  a  very 
great,  if  not  preponderating,  influence. 

The  truth  seems  to  be  that  the  character  of  a  particular  grape  grown 
under  particular  conditions  determines  the  class  of  wine  which  can  best 
be  made  from  it,  and  also  fixes  a  certain  maximum  quality  which  its 
wine  can  be  made  to  approach  by  perfecting  the  methods  of  manufacture. 

Wine  is  one  of  the  most  complex  and  diverse  of  manufactured  prod- 
ucts, and  the  processes  of  manufacture  must  be  equally  diverse  if  we  are 
to  reach  in  each  case  the  maximum  possible  quality.  The  processes  must 
vary  according  to  the  composition  of  the  grape,  its  contents  of  sugar, 
acid,  color,  flavor,  and  mineral  salts ;  according  to  the  varying  temper- 
ature of  the  vintage  in  various  seasons  and  localities ;  according  to  the 
micro-organisms,  molds,  yeasts  and  bacteria,  which  occur  in  varying 
numbers  and  kinds,  and,  finally,  according  to  the  class  of  wine,  fine  or 
common,  white  or  red,  dry  or  sweet,  still  or  sparkling,  which  it  is 
desired  to  make. 

The  most  important  part  of  the  manufacturing  process  is  the  fermen- 
tation. It  is  precisely  this  part  which  has  been  the  last  to  be  brought 
under  proper  control  and  in  which  wine-makers  are  slowest  in  estab- 
lishing that  logical  practice  which  alone  can  give  certainty  to  the  results. 

The  handling  of  a  properly  fermented  wine  is  simple,  easy  and  under- 
stood by  all  good  cellarmen.    An  improperly  fermented  wine  is  never 


406  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

a  good  wine,  and  to  save  it  from  spoiling  and  becoming  a  dead  loss 
taxes  the  ingenuity  and  skill  of  the  most  experienced  wine-handlers. 
A  wine  is  practically  made  or  spoiled  in  the  fermenting  vat  or  cask. 
The  most  critical  period  is  the  first  week  of  the  life  of  the  wine;  that  of 
the  "main  fermentation."  An  almost  equally  important  period  is  the 
following  month  or  six  weeks;  that  of  the  "after  fermentation."  A 
wine,  which  passes  successfully  through  these  two  periods  is  almost 
"fool-proof."  A  wine,  neglected  or  improperly  treated  during  these 
periods  is  a  cripple  for  life. 

In  the  rush  of  the  vintage  season,  the  average  cellarman  's  main  preoc- 
cupation is  to  change  the  grapes  from  the  solid  condition  in  boxes  to 
the  liquid  condition  in  casks.  After  the  last  load  of  grapes  is  crushed 
he  examines  his  wine,  commences  to  nurse  it  or  calls  in  the  doctor.  It 
is  then  too  late.  The  best  he  can  do  is  to  pick  out  the  casks  he  can  foist 
on  his  customers  and  distil  the  rest. 

(&)  Outline  of  the  Operations  of  Wine-making. — The  operations  in 
the  production  of  wine  take  place  in  four  more  or  less  distinct  stages, 
all  necessary  for  the  final  result. 

The  first  is  the  production  of  the  grapes,  which  is  the  province  of 
viticulture.  Unless  this  is  properly  done,  however,  the  work  of  the 
wine-maker  becomes  difficult  or  impossible.  Suitable  varieties  of  grapes 
must  be  grown  and  they  must  be  brought  to  the  proper  degree  of  ripeness 
free  from  injury  or  decay  before  they  are  delivered  to  the  wine-maker. 

The  second  stage  is  the  transfer  of  the  grapes  to  the  fermenting  vat 
or  cask.  However  good  the  fruit  is  on  the  vine  it  may  be  spoiled  in  this 
transfer.  The  grapes  must  be  gathered  intelligently  and  skillfully ;  they 
must  be  stored  and  transporated  with  as  little  injury  as  possible ;  they 
must  be  protected  from  dirt,  mold,  and  injurious  fermentation;  they 
must  be  handled  in  a  cleanly  and  efficient  manner  in  boxes,  wagons, 
conveyors,  crushers  and  must  lines. 

The  third  stage,  that  of  fermentation,  is  usually  considered  the  most 
important  because  it  is  at  this  stage  that  most  wine  is  spoiled.  If  this 
stage  is  skillfully  conducted,  fair  wine  may  be  made  even  from  inferior 
grapes,  while  mistakes  at  this  stage  will  spoil  the  best.  The  alcoholic 
fermentation  is  the  breaking  up  of  the  sugar  and  the  production  of 
alcohol.  At  the  same  time  color  and  tannin  are  extracted  from  the 
skins  and  various  minor  changes  occur. 

The  final  stage  is  the  aging  of  the  wine.  This  consists  of  two  more 
or  less  concurrent  changes,  the  clearing  of  the  wine  by  the  elimination 
and  precipitation  of  all  undissolved  matters  and  the  acquirement  of 
certain  desired  flavors  through  gradual,  slow  oxidation. 

(c)  The  Relation  of  Micro-organisms  to  Wine-making. — Throughout 
all   these  stages  the  grapes  and  wine  are  liable  to  be  influenced  by  a 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKING.  407 

great  number  of  micro-organisms.  In  fact,  the  whole  art  of  the  wine- 
maker,  as  distinct  from  that  of  the  grape-grower,  may  be  looked  upon 
as  the  control  of  the  various  agents  of  fermentation.  A  clear  under- 
standing of  the  nature  of  these  agents  and  of  the  means  by  which  they 
can  be  controlled  is  a  necessary  and  the  most  essential  part  of  the  equip- 
ment of  the  wine-maker.     The  rest  is  little  more  than  mechanical  skill. 

(d)  Causes  of  Fermentation. — If  we  crush  grapes  and  place  them  in 
a  vat,  as  is  usually  done  in  ordinary  wine-making,  they  go  through 
certain  changes.  Bubbles  of  carbonic  acid  gas  are  given  off,  the  sugar 
disappears  more  or  less  completely  and  alcohol  and  other  substances  are 
formed.     These  phenomena  are  called  fermentation. 

The  fermentation  proceeds  in  different  ways  in  different  cases  and 
the  resulting  wine  varies  very  much  in  character  even  when  the  grapes 
are  apparently  identical.  The  reason  of  these  differences  is  that  the 
causes  of  fermentation  are  not  always  the  same. 

Fermentations  of  all  kinds  are  due  to  the  action  of  microscopic 
6 '  plants ' ' :  yeasts,  molds  and  bacteria,  of  which  there  are  innumerable 
kinds.  In  wine-making,  they  are  all  bad  except  one.  This  one  is  the 
true  wine  yeast,  known  botanically  as  Saccharomyces  ellipsoideus. 

If  we  examine  freshly  expressed  grape  juice  under  a  microscope, 
magnifying  200-300  diameters,  we  will  usually  find  no  bacteria  and  no 
yeast,  and  at  most,  a  few  molds.  If  we  examine  it  again,  after  bubbles 
of  gas  have  commenced  to  come  off  we  will  find  large  numbers  of  various 
kinds  of  yeasts  and  molds.  When  the  fermentation  is  nearly  over, 
especially  if  the  temperature  has  been  high,  another  examination  will 
reveal  large  numbers  of  bacteria  among  the  other  micro-organisms. 

These  observations  prove  two  important  facts.  First,  that  the  germs 
of  many  kinds  of  fermenting  micro-organisms  are  present  on  the  grapes 
when  they  are  crushed,  but  in  comparatively  small  numbers,  so  that 
they  can  not  be  found  readily  by  simple  observation.  Second,  that 
many  of  these  micro-organisms  develop  in  large  numbers  but  with 
different  degrees  of  rapidity. 

Whether  the  wine  will  be  sound  or  will  spoil,  whether  it  will  reach 
the  maximum  quality  possible  for  the  raw  material,  depends  on  the  kind 
of  microbial  growth  which  occurs  in  the  fermenting  mass.  The  skillful 
wine-maker  can  control  the  kind  and  amount  of  this  growth ;  the  unskill- 
ful leaves  it  to  chance.  In  order  to  exercise  this  control,  the  wine- 
maker  must  understand  the  micro-organisms  with  which  he  is  dealing. 
He  must  know  what  they  are  like,  where  they  come  from,  what  condi- 
tions favor  their  multiplication.  When  he  possesses  this  knowledge, 
many  parts  of  his  art  which  seemed  difficult  or  mysterious  are  seen  to  be 
perfectly  simple  and  under  almost  absolute  control. 

2— b213 


408  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

IV.    MICRO-ORGANISMS  FOUND  ON  GRAPES. 

On  the  surfaces  of  grapes  in  the  vineyard  may  be  found  any  of  the 
bacteria  and  fungi  usually  carried  by  the  air  and  by  insects.  Many  of 
these,  especially  of  the  bacteria,  are  incapable  of  growing  in  grape  juice 
on  account  of  its  high  acidity.  They  are,  therefore,  negligible  and 
without  effect  on  the  wine.  Others,  such  as  most  yeasts  and  molds  and 
a  few  bacteria,  find  in  grape  juice  a  very  favorable  medium  for  develop- 
ment and  growth.  Wine  is  a  less  favorable  medium  than  must  (grape 
juice),  owing  to  the  alcohol  it  contains,  but  still,  a  large  number  of 
forms  are  capable  of  developing  also  in  the  wine.  The  older  the  wine 
becomes  the  less  suitable  it  is  for  the  growth  of  micro-organisms,  but  it 
is  never  quite  immune. 

(a)  Molds. — The  spores  of  the  common  saprophytic  molds,  Penicil- 
lium,  Aspergillus,  Mucor,  Dematium,  are  always  present  on  the  grapes, 
boxes,  and  crushers,  as  on  all  surfaces  exposed  to  dust  laden  air,  and 
most  of  them  find  in  grape  must,  excellent  conditions  for  development. 
Botrytis  cinerea,  a  facultative  parasite  of  the  leaves  and  fruit  of  the 
vine,  is  also  nearly  constantly  present  in  larger  or  smaller  quantities. 
All  of  these  molds  are  harmful,  in  varying  degrees,  to  the  grapes  and 
the  wine.  Some  of  them,  such  as  Penicillium,  may  give  a  disagreeable 
moldy  taste  of  the  wine,  sufficient  to  spoil  its  commercial  value.  Others, 
such  as  Mucor  and  Aspergillus  may  affect  the  taste  of  the  wine  but 
slightly  and  injure  it  only  by  destroying  some  of  the  sugar  and  thereby 
diminishing  the  alcohol.  Dematium  pullulans  may  produce  a  slimy 
condition  in  weak  white  musts,  and  most  of  them  injure  the  brightness 
and  flavor  to  some  extent  and  often  render  the  wine  more  susceptible 
to  the  attacks  of  more  destructive  forms  of  micro-organisms. 

On  sound,  ripe  grapes,  these  molds  occur  in  relatively  small  number, 
and,  being  in  the  spore  or  dormant  condition,  they  are  unable  to  develop 
sufficiently  to  injure  the  wine  under  the  conditions  of  proper  wine- 
making.  On  grapes  which  are  injured  by  diseases,  insects  or  rain, 
they  may  be  present  in  sufficient  quantities  to  spoil  the  crop  before  it  is 
gathered.  On  sound  grapes  which  are  gathered  and  handled  carelessly, 
they  may  develop  sufficiently  before  fermentation  to  injure  or  spoil  the 
wine. 

The  molds  are  recognized  by  their  white  or  greyish  cobwebby  growth 
over  the  surface  of  the  fruit.  This  consists  of  fine  branching  and  inter- 
lacing filaments  known  as  mycelium.  This  is  the  vegetative  stage  of  the 
fungus,  and  the  active  pari  in  the  destruction  of  the  material  attacked. 
When  mature,  it  produces  spores  which  differ  for  each  mold  in  form, 
siz<-  and  color.  The  spores  are  the  chief  means  of  multiplication  and 
distribution.  They  are  minute,  single  celled  bodies  which  are  easily 
distributed  like  dusl  through  the  air,  and  are  capable,  after  remaining 
dormant  for  a  longer  or  shorter  period,  of  germinating,  under  favorable 
conditions,  and  giving  rise  to  ;i  now  growth  of  mycelium. 


Bulletin  213]  the  principles  of  wine-making. 


409 


Fig.  1. — Grape  mold's  injurious  to  wine. 

I.     Black  mold   {Aspergillus  niger).      (After  Duclauxj 

a.  Fruiting  hyphae. 

b.  Sporecarp  showing  formation  of  spores. 

c.  Spores  enlarged. 

II.     Gray  mold  (Botrytis  cinerea).      (After  Ravaz.) 
III.     Blue  mold   (Penicillinm  glaucuvi) .      (From  skin  of  moldy  grape.) 

a.  Mycelium  or  vegetative  part. 

b.  Fruiting  hypha. 

c.  Chains  of  spores. 

d.  Spores  enlarged. 


410  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 

The  commonest  molds  on  grapes  in  California  are  the  Blue  Mold,  the 
Black  Mold,  and  the  Gray  Mold.  Usually  only  one  of  these  occurs 
plentifully  at  the  same  time.  "Which  this  one  will  be  depends  princip- 
ally upon  the  temperature  and  humidity.  In  the  hotter  regions  the 
Black  Mold  is  most  common  during  the  earlier  part  of  the  vintage,  later 
the  Blue  Mold  takes  its  place.  In  the  cooler  regions  only  Gray  and  Blue 
Molds  occur  commonly. 

(1)  Blue  Mold  (Penicillium  glaucum).  This  is  the  common  mold 
which  attacks  all  kinds  of  fruit  and  foods  kept  for  a  length  of  time  in  a 
damp  place.  It  is  distinguished  by  the  greenish  or  bluish  color  of  its 
spores  which  cover  the  grapes  attacked,  and  by  its  strong  disagreeable 
moldy  smell.  It  sometimes  attacks  late  grapes  in  the  vineyard  after 
autumn  rains  have  caused  some  of  them  to  split.  Grapes  lying  on  the 
ground  are  especially  liable  to  attack.  The  principal  damage  of  this 
mold  occurs  usually  after  the  grapes  are  gathered  while  they  lie  in  boxes 
or  other  containers.  It  will  grow  on  almost  any  organic  matter  if  sup- 
plied with  sufficient  moisture  and  at  almost  any  ordinary  temperature. 
It  is  almost  the  sole  cause  of  all  moldiness  in  boxes,  hoses  and  casks,  and 
the  most  troublesome  of  all  the  molds  with  which  the  wine-maker  has 
to  deal. 

The  conditions  most  favorable  to  its  development  are  an  atmosphere 
saturated  with  moisture  and  the  presence  of  oxygen. 

(2)  Black  Mold  (Aspergillus  niger).  This  is  very  common  in  the 
hotter  and  irrigated  parts  of  California.  It  annually  destroys  many 
tons  of  grapes  before  they  are  gathered.  It  attacks  the  grapes  just  as 
they  ripen  and  is  distinguished  by  the  black  color  of  its  spores,  which 
sometimes  fill  the  air  with  a  black  cloud  at  the  wineries  where  the  grapes 
are  being  crushed.  It  is  especially  harmful  to  varieties  which  have 
compact  bunches  and  thin  skins,  such  as  Zinfandel.  Its  effect  on  the 
wine  has  not  been  well  studied  but  it  is  much  less  harmful  than  Green 
Mold.  Large  quantities  of  grapes  badly  attacked  are  made  every  year 
into  merchantable  wine.  The  main  damage  done  is  in  the  destruction 
of  crop  and  it  is  therefore  a  greater  enemy  to  the  grape-grower  than  to 
the  wine-maker. 

(3)  Gray  Mold  (Botrytis  cinerea).  This  fungus  in  certain  parts  of 
Europe  is  a  harmful  parasite  of  the  vine,  injuring  seriously  leaves, 
shoots  and  growing  fruit.  The  only  injury  of  this  kind  noted  in  Cali- 
fornia is  in  the  "callusing"  beds  of  bench  grafts. 

As  a  saprophyte  it  may  attack  the  ripe  grapes  in  much  the  same  man- 
ner as  the  Black  Mold.  It  occurs  apparently  all  over  California  but 
seldom  does  much  damage.  It  attacks  principally  second  crop  and  late 
table  grapes. 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKING.  411 

Under  certain  circumstances  this  fungus  may  have  a  beneficial  action. 
When  the  condition  of  temperature  and  moisture  are  favorable,  it  will 
attack  the  skin  of  the  grape,  facilitating  evaporation  of  water  from 
the  pulp.  This  results  in  a  concentration  of  the  juice.  The  mycelial 
threads  of  the  fungus  then  penetrate  the  pulp,  consuming  both  sugar 
and  acid  but  principally  the  latter.  The  net  result  is  an  increase  in  the 
percentage  of  sugar  and  a  decrease  in  that  of  acid.  This,  where  grapes 
ripen  with  difficulty,  is  an  advantage,  as  no  moldy  flavor  is  produced. 
Two  harmful  effects,  however,  follow:  first,  the  growth  of  the  mold 
results  in  the  destruction  of  a  certain  amount  of  material  and  a  conse- 
quent loss  of  quantity.  This  is,  in  certain  circumstances,  more  than 
counterbalanced  by  an  increase  in  quality.  This  is  the  case  with  the 
finest  wines  of  the  Rhine  and  Sauternes.  For  this  reason,  the  fungus 
is  called  in  those  regions  the  "Noble  Mold."  Second,  an  oxydase  is  pro- 
duced which  tends  to  destroy  the  color,  brightness  and  flavor  of  the  vine. 
This  can  be  counteracted  by  the  judicious  use  of  sulfurous  acid. 

This  mold  is  not  of  great  importance  in  California  as  we  do  not  need 
its  beneficial  effects  and  it  is  seldom  abundant  enough  to  do  much  harm. 

(&)  Yeasts. — The  true  yeasts  occur  much  less  abundantly  on  grapes 
than  the  molds.  Until  the  grapes  are  ripe  they  are  practically  absent, 
as  first  shown  by  Pasteur.  Later,  they  gradually  increase  in  number; 
on  very  ripe  grapes  being  often  abundant.  In  all  cases  and  at  all 
seasons,  however,  their  numbers  are  much  inferior  to  those  of  the  molds 
and  pseudo-yeasts.  The  cause  of  this  seems  to  be  that,  in  the  vineyard, 
the  common  molds  find  conditions  favorable  to  their  development  at 
nearly  all  seasons  of  the  year,  but  yeasts  only  during  the  vintage  season. 

Investigations  of  Hansen,  Wortmann  and  others  show  that  yeasts 
exist  in  the  soil  of  the  vineyard  at  all  times,  but  in  very  varying 
amounts.  For  a  month  or  two  following  the  vintage,  a  particle  of  soil 
added  to  nutritive  solution  contains  so  much  yeast  that  it  acts  like  a 
leaven.  For  the  next  few  months  the  amount  of  yeast  present  decreases 
until  a  little  before  the  vintage,  when  the  soil  must  be  carefully  exam- 
ined to  find  any  yeast  at  all.  As  soon  as  the  grapes  are  ripe,  however, 
any  rupture  of  the  skin  of  the  fruit  will  offer  a  favorable  nidus  for  the 
development  and  increase  of  any  yeast  cells  which  reach  it.  Where  these 
first  cells  come  from  has  not  been  determined,  but  as  there  are  still  a 
few  yeast  cells  in  the  soil,  they  may  be  brought  by  the  wind,  or  bees  and 
wasps  may  carry  them  from  other  fruits  or  from  their  hives  and  nests. 

The  increase  of  the  amount  of  yeast  present  on  the  ripe  grapes  is 
often  very  rapid  and  seems  to  have  (according  to  Wortmann)  a  direct 
relation  to  the  abundance  of  wasps.  These  insects  passing  from  vine  to 
vine,  crawling  over  the  bunches  to  feed  on  the  juice  of  ruptured  berries, 
soon  inoculate  all  exposed  juice  and  pulp.     New  yeast  colonies  are  thus 


412  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

produced  and  the  resulting  yeast  cells  quickly  disseminated  over  the 
skins  and  other  surfaces  visited. 

The  more  unsound  or  broken  grapes  present,  the  more  honey  dew  or 
dust  adhering  to  the  skins,  the  larger  the  amount  of  yeast  will  be.  The 
same  is  true,  however,  also  of  molds  and  other  organisms. 

True  Yeasts:  Saccharomyces. — The  true  yeasts  differ  from  the  molds 
in  the  absence  of  a  true  mycelium  and  in  a  different  method  of  spore 
formation.  They  constitute  several  botanical  groups  or  genera  of  which 
only  one,  Saccharomyces,  is  of  practical  importance  to  the  wine-maker. 
This  genus  consists  of  unicellular  fungi,  multiplying  by  budding. 
Under  certain  conditions  some  or  all  of  the  cells  may  produce  spores 
in  their  interior.  Such  cells  are  called  asci,  and  the  contained  spores 
asco-spores,  or  endospores. 

1.  Nutrition.  The  preferred  food  of  the  yeasts  is  the  sweet  juice  of 
more  or  less  acid  fruits.  Most  of  them  are  active  agents  of  alcoholic 
fermentation  breaking  up  the  sugar  into  alcohol  and  carbonic  acid  gas. 
Wine  yeast  may  carry  on  the  fermentation  until  the  liquid  contains 
15  per  cent  or  slightly  more  of  alcohol.  Other  yeasts,  such  as  ordinary 
beer  yeast  cease  their  activity  when  the  alcoholic  strength  of  the  liquid 
reaches  8  to  10  per  cent,  while  some  wild  yeasts  are  restrained  by 
2  to  3  per  cent. 

2.  E elation  to  Oxygen.  They  are  aerobic,  that  is,  they  require  the 
oxygen  of  the  air  for  their  development.  Most  of  them  are,  however, 
capable  of  living  and  multiplying  for  a  limited  time  in  the  anaerobic 
condition,  that  is,  in  the  absence  of  atmospheric  oxygen.  It  is  in  the 
latter  condition  that  they  exhibit  their  greatest  power  of  alcoholic 
fermentation.  They  multiply  most  rapidly  and  attain  their  greatest 
vigor  in  the  presence  of  a  full  supply  of  air.  In  wine-making,  therefore, 
it  is  necessary,  first,  to  promote  their  multiplication  and  vigor  by  grow- 
ing in  a  nutritive  solution  containing  a  full  supply  of  oxygen  and,  then, 
to  make  use  of  their  numbers  and  vigor  to  produce  alcoholic  fermenta- 
tion in  a  saccharine  solution  containing  a  limited  supply  of  oxygen. 
These  conditions  are  brought  about  automatically  in  the  usual  methods 
of  wine-making.  The  crushing  and  stemming  of  the  grapes  thoroughly 
aerates  the  must.  The  yeast  multiplies  vigorously  in  this  aerated 
nutritive  solution  until  it  has  consumed  most  of  the  dissolved  oxygen. 
11  then  exercises  its  fermentative  power  to  break  up  the  sugar,  with 
the  production  of  alcohol.  With  many  musts  it  is  able  in  this  way  to 
completely  destroy  all  the  sugar  without  further  oxygen.  In  other 
musts,  cspeeially  those  containing  a  high  percentage  of  sugar,  the  yeast 
becomes  debilitated  before  the  wine  is  dry.  In  such  cases  it  is  generally 
necessary  to  reinvigorate  ii  by  pumping  the  wine  over  or  oilier  method 
of  aeration  before  ii  can  complete  ils  work. 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  413 

3.  Relation  to  Temperature.  Yeast  cells  can  not  be  killed  or  appre- 
ciably injured  by  any  low  temperature.  They  do  not  become  active, 
however,  until  the  temperature  exceeds  32°F.  "Wine  yeast  shows 
scarcely  any  activity  below  50°  F.  and  multiplies  very  slowly  below 
60°  F.  Above  this  temperature  the  activity  of  the  yeast  gradually 
increases.  Between  70°  F.  and  80°  F.  it  is  very  active  and  it  attains 
its  maximum  degree  of  activity  between  90°  F.  and  93°  F.  Above 
93°  F.  it  is  weakened,  and  between  95°  F.  and  100°  F.  its  activity 
ceases.  At  still  higher  temperatures  the  yeast  cell  dies.  The  exact 
death  point  depends  on  the  condition  of  the  yeast,  the  nature  of  the 
solution  and  the  time  of  exposure.  In  must  and  wine  a  temperature 
of  140°  F.  to  145°  F.  continued  for  one  minute  is  usually  enough  to 
destroy  the  yeast. 

The  best  temperature  in  wine-making  will  depend  on  the  kind  of  wine 
to  be  made  and  will  lie  between  70°  F.  and  90°  F. 

4.  Relation  to  Acids.  The  natural  acids  of  the  grapes,  in  the  amounts 
in  which  they  occur  in  must,  have  little  direct  effect  on  wine  yeast. 
Indirectly  they  may  be  favorable  by  discouraging  the. growth  of  com- 
peting organisms  more  sensitive  to  acidity.  Acetic  acid  has  a  strong 
retarding  influence  which  commences  at  about  .2  per  cent  and  increases 
with  larger  amounts  until  at  .5  per  cent  to  1  per  cent  according  to  the 
variety  of  the  yeast,  all  activity  ceases. 

5.  Relation  to  Sulfurous  Acid.  The  fumes  of  burning  sulfur  are 
used  in  various  ways  and  for  various  purposes  in  wine-making.  The 
active  principle  of  these  fumes  is  sulfurous  acid  gas  of  which  the  chem- 
ical formula  S02  shows  that  it  is  composed  of  one  atom  of  sulfur  com- 
bined with  two  atoms  of  oxygen*.  As  sulfur  has  just  twice  the  atomic 
weight  of  oxygen  this  means  that  one  part  by  weight  of  sulphur 
combines  with  one  part  by  weight  of  oxygen  to  produce  two  parts  by 
weight  of  sulfurous  acid  gas.  This  combination  takes  place  when  sulfiir 
is  burned  in  free  contact  with  air.  The  same  substance  can  be  obtained 
from  certain  salts,  only  one  of  which  is  suitable  for  use  in  wine-making. 
This  is  a  potash  salt  known  as  potassium  meta-bisulftte.  This  salt  is 
composed  of  nearly  equal  weights  of  potash  and  sulfurous  acid.  In 
contact  with  the  acids  of  the  must,  the  sulfurous  acid  is  set  free  and  the 
potash  combines  with  the  tartaric  acid  of  the  must  to  form  bi-tartrate  of 
potash,  which  is  already  a  constituent  of  the  natural  must. 

Sulfurous  acid  is  an  antiseptic,  mild  or  strong,  according  to  the 
quantities  present.  Bacteria  of  all  kinds  are  much  more  sensitive  to  its 
effects  than  yeasts.  If  used,  therefore,  in  properly  regulated  amounts  it 
can  be  made  a  very  efficient  means  of  preventing  bacterial  action  and 
thus  indirectly  of  aiding  the  work  of  the  yeast.  It  has  also  the  very 
valuable  property  of  preventing  the  injurious  action  of  the  oxydase 


414 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 


produced  by  Botrytis  and  other  molds.  Finally,  it  is  necessary  in  most 
cases  to  prevent  the  too  rapid  or  overoxidization  of  the  wine  during 
aging. 

6.  Morphology  of  Wine  Yeasts. — The  yeasts,  like  the  molds,  are 
fungi,  but  they  are  single  celled  and  without  a  filiform  mycelium. 
Wine  yeast  consists  of  cells  so  small  that  it  would  require  about  2,500 
placed  end-to-end  to  stretch  one  inch.  They  can  be  seen  individually 
only  by  means  of  a  high  power  microscope.     In  masses  they  may  be 


0 


o    <g&     $     Q 


®  §  8  ©  «  ( 


0 


6<? 

0 


\if 


eb. 


Fig.  2. — Wine  yeast. 

1.  Saccharomyces  ellipsoideus,  young. 

2.  Saccharomyces  ellipsiodeus,  old. 

3.  Saccharomyces  ellipsoideus,  spores. 

4.  Mixed  forms  of  yeast  cells  in  fermenting  grape  juice. 


seen  in  the  sediment  of  the  fermenting  liquids  as  a  fine,  smooth,  or 
somewhat  granular  powder.  In  the  body  of  the  liquid  they  produce 
more  or  less  cloudiness  according  to  their  number. 

Under  the  microscope,  the  cells  are  seen  to  be  spherical,  ellipsoidal,  or 
oval  bodies  consisting  of  a  thin  outside  membrane — the  cell  wall,  enclos- 
ing the  cell  contents.  In  young  cells,  the  contents  appear  translucent 
and  almost  homogeneous,  but,  when  older,  various  clear  space  {vacuoles) 
and  dark  bodies  {granules)  appear.  Very  old  and  dead  cells  are  very 
granular  and  almost  opaque.  Yeast  cells  multiply  by  budding.  Under 
conditioDs  favorable  to  growth,  a  small  rounded  swelling  appears  near 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKING.  415 

one  end  of  the  cell.  This  gradually  increases  in  size,  forms  a  partition 
that  separates  its  contents  from  those  of  the  mother  cell  and  finally 
develops  to  full  size,  thus  forming  a  new  yeast  cell.  The  daughter  cell 
usually  separates  immediately,  and  buds  in  turn.  The  production  of 
a  new  cell  requires,  under  favorable  conditions,  from  one  to  several 
hours.  Yeast  cells  may,  therefore,  increase  a  million  fold  in  twenty- 
four  hours. 

When  young,  vigorous,  well  nourished  cells  are  supplied  with  abun- 
dant air  and  moisture  at  a  comparatively  high  temperature  under  condi- 
tions that  discourage  budding  (lack  of  nutriment)  they  form  endospores. 
These  spores  are  about  half  the  diameter  of  the  mother  cell  and  from 
one  to  four  usually  occur  in  a  cell.  They  are  more  opaque  than  the 
other  cell  contents  and  can  be  distinguished  from  the  granules  by  their 
uniformity  of  size  and  shape.  They  are  not  formed  in  the  must  or 
wine. 

In  the  older  wine-making  districts,  much  of  the  yeast  present  on  the 
grapes  consists  of  the  true  wine  yeast,  S.  ellipsoideus.  The  race  or 
variety  of  this  yeast  differs,  however,  in  different  districts.  Usually 
several  varieties  occur  in  each  district.  The  idea  prevalent  at  one  time, 
that  each  variety  of  grape  has  its  own  variety  of  yeast  seems  to  have 
been  disproved,  though  there  seems  to  be  some  basis  for  the  idea  that 
grapes  differing  very  much  in  composition,  varying  in  acidity  and 
tannin  contents,  may  vary  also  in  the  kind  of  yeast  present.  Several 
varieties  of  ellipsoideus  may  occur  on  the  same  grapes.  In  new  grape- 
growing  districts,  where  wine  has  never  been  made,  ellipsoideus  may 
be  completely  absent. 

Besides  the  true  wine  yeast,  other  yeasts  usually  occur.  The  com- 
monest forms  are  cylindrical  cells  grouped  as  S.  pasteurianus.  These 
forms  are  particularly  abundant  in  the  newer  districts,  where  they 
may  take  a  notable  part  in  the  fermentation.  Their  presence  in  large 
numbers  is  always  undesirable,  and  results  in  inferior  wine.  Many 
other  yeasts  may  occur  occasionally,  and  are  all  more  or  less  harmful. 
Some  have  been  noted  as  producing  sliminess  in  the  wine.  Many  of 
these  yeasts  produce  little  or  no  alcohol  and  will  grow  only  in  the 
presence  of  oxygen. 

(c)  Pseudo-yeasts. — Yeast-like  organisms  producing  no  endospores 
always  occur  on  grapes.  Their  annual  life  cycle  and  their  distribution 
are  similar  to  those  of  the  true  yeasts  but  some  of  them  are  much  more 
abundant  than  the  latter.  They  live  at  the  expense  of  the  food  mate- 
rials of  the  must  and,  when  allowed  to  develop,  cause  cloudiness  and 
various  defects  in  the  wine. 

The  most  important  and  abundant  is  the  apiculate  yeast  S.  apiculatus, 
(according  to  Lindner  this  is  a  true  yeast,  producing  endospores) .  The 
cells  of  this  organism  are  much  smaller  than  those  of  8.  ellipsoideus  and 


416 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


very  distinct  in  form.  In  pure  cultures  these  cells  show  various  forms, 
ranging  from  ellipsoidal  to  pear-shaped  (apiculate  at  one  end)  and 
lemon-shaped  (apiculate  at  both  ends).  These  forms  represent  simply 
stages  of  development.  The  apiculations  are  the  first  stage  in  the  forma- 
tion of  daughter  cells;  the  ellipsoidal  cells,  the  newly  separated  daughter 
cells,  which,  later,  produce  apiculations  and  new  cells  in  turn. 

Many  varieties  of  this  yeast  occur,  similar  in  degree  to  those  of 
S.  ellipsoideus.  They  are  widely  distributed  in  nature,  occuring  on 
most  fruits,  and  are  particularly  abundant  on  acid  fruits  such  as  grapes. 
Apiculate  yeast  appears  on  the  partially  ripe  grapes  before  the  true 


<^ 


a 


>^ji 


Fig.   3. — Yeasts  and  pseudo-yeasts  injurious  to  wine. 

Saccharomyces  apiculatus. 
Saccharomyces  pasteurianus. 
Mycoderma  vini    (2  forms). 
Dematium  pullulans. 
Torulae  and  pseudo-yeasts. 
Torulse  and  pseudo-yeasts. 


wine  yeast  and  even  on  ripe  grapes  is  more  abundant  than  the  latter. 
Tin-  rate  of  multiplication  of  this  yeast  is  very  rapid  under  favoring 
conditions  and  much  exceeds  that  of  wine  yeast.  The  first  part  of 
the  fermentation,  especially  at  the  beginning  of  the  vintage  and  with 
acid  grapes,  is.  therefore,  often  almost  entirely  the  work  of  the  apiculate 

The  amount  of  alcohol  produced  by  this  yeast  is  about  4  per  cent, 
varying  with  the  variety  from  2  to  6  per  cent.  When  the  fermentation 
has  produced  this  amount  of  alcohol,  the  activity  of  the  yeast  slackens 
and  finally  stops,  allowing  the  more  resistant  ellipsoideus  to  multiply 
and  finish  the  destruction  of  the  sugar.  The  growth  of  the  apiculatus, 
however,  has  a  deterring  effect  on  that  of  the  true  yeast  so  that  where 
much  of  the  former  lias  been   present,  during  the  first  stages  of  the 


Bulletin  213]  the  principles  oi^  wine-making.  417 

fermentation,  the  latter  often  fails  to  eliminate  all  the  sugar  during 
the  last  stages. 

Wines  in  which  the  apiculate  yeast  has  had  a  large  part  in  the 
fermentation  are  apt  to  retain  some  unfermented  sugar  and  are  very 
liable  to  the  attacks  of  disease  organisms.  Their  taste  and  color  are 
defective,  often  suggestive  of  cider  and  they  are  difficult  to  clear. 
This  yeast  attacks  the  fixed  acids  of  the  must,  the  amount  of  which  is 
therefore  diminished  in  the  wine  while,  on  the  other  hand,  the  volatile 
acids  are  increased. 

Many  other  yeast-like  organisms  may  occur  on  grapes  but,  under 
ordinary  conditions,  fail  to  develop  sufficiently  in  competition  with 
apiculatus  to  have  any  appreciable  effect  on  the  wine.  Most  of  them 
are  small  round  cells,  classed  usually  as  Torulae.  They  destroy  the 
sugar  but  produce  little  or  no  alcohol. 

A  group  of  similar  forms,  known  collectively  as  Mycoderma  vim'. 
occurs  constantly  on  the  grapes  but,  all  being  strongly  aerobic,  they  do 
not  develop  in  the  fermenting  vat,  but,  under  favoring  conditions,  may 
be  harmful  to  the  fermented  wine. 

(d)  Bacteria  of  many  kinds  occur  on  grapes  as  on  all  surfaces  exposed 
to  the  air.  Most  of  these  are  unable  to  develop  in  solutions  as  acid  as 
grape  juice  of  wine.  Of  the  acid-resisting  kinds,  a  number  may  cause 
serious  defects  and  even  completely  destroy  the  wine.  These,  the 
'"disease  bacteria"  of  wine  are  mostly  anaerobic  and  can  develop  only 
after  the  grapes  are  crushed  and  the  oxygen  of  the  must  exhausted  by 
other  organisms.  Practically  all  grape-must  contains  some  of  these 
bacteria,  which,  unless  the  work  of  the  wine-maker  is  properly  done, 
will  seriously  interfere  with  the  work  of  the  yeast,  and  may  finally 
spoil  the  wine.  The  only  bacteria  which  may  injure  the  grapes  before 
crushing  are  the  aerobic,  vinegar  bacteria,  which  may  develop  on  injured 
or  carelessly  handled  grapes  sufficiently  to  interfere  with  fermentation 
and  seriously  impair  the  quality  of  the  wine. 


V.    MICRO-ORGANISMS  FOUND  IN  WINE. 

Wine  micro-organisms  may  be  conveniently  divided  into  two  groups : 
Those  which  grow  only  in  the  presence  of  notable  supplies  of  free  oxygen 
at  robic),  and  those  which  require  or  grow  better  in  the  absence  of  free 
oxy gen  ( anaerobic ) . 

(a)  Aerobic  organisms.  1.  Mycodermce.  If  a  normal  wine,  especially 
one  strong  in  alcohol,  is  left  with  its  surface  exposed  to  the  air,  it  will 
usually,  in  a  few  days,  be  covered  with  a  whitish  film,  thin  and  smooth 
at  first  but  gradually  becoming  thicker  and  finally  rough  and  plicate. 


418 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


This  is  what  is  known  to  wine-makers  as  "wine  floivers."  This  film 
consists  of  yeast-like  cells,  somewhat  longer  and  more  cylindrical  and 
regular  than  S.  ellipsoideus,  reproducing  by  budding  and  forming  large 
aggregations. 

Pure  cultures  show  that  there  are  many  varieties  of  this  organism 
differing  in  the  color  and  texture  of  the  film,  in  the  cloudiness  of  the 
liquid  and  the  character  of  the  deposit.  They  are  called  collectively 
Mycoderma  vini. 

These  organisms  are  strongly  aerobic  and  can  develop  only  on  the 


^ 


\  / 


Fig.  4. — Bacteria  of  wine  diseases. 

1.  Bacteria  of  vinegar — sour  wine  (acetic). 

2.  Bacteria  of  lactic  wine  (propionic),  young, 
(a)    Cell  of  wine  yeast. 

3.  Bacteria  of  lactic  wine   (propionic),  old. 

4.  Bacteria  of  slimy  wine. 

5.  Bacteria  of  mannitic  wine. 

6.  Bacteria  of  bitter  wine  (butyric). 

surface  in  full  contact  with  the  air.  They  are  a  serious  enemy  to  the 
wine,  rendering  it  insipid  and  cloudy.  They  attack  the  extract,  fixed 
acids  and  alcohol,  producing  at  first  volatile  acids  and  finally  causing 
complete  combustion  of  the  organic  matters  to  C02  and  H20,  destroying 
the  wine  completely. 

2.  Acetic  Bacteria.  The  film  formed  on  wines  exposed  to  the  air, 
especially  on  those  of  low  alcoholic  contents,  will  often  differ  from  that 
due  to  Mycoderma  vini.  It  will  be  thinner,  smoother  and  consist  of 
bacteria.  These,  the  acetic  bacteria,  grow  not  only  on  the  wine  at  the 
expense  of  the  alcohol,  but  on  crushed  grapes  and  must  at  the  expense 
of  the  sugar,  producing  acetic  acid  in  both  cases. 

Acetic  acid  in  small  amounts  is  a  normal  constituent  of  wine  produced 
by  the  yeast.  Unless  in  excess,  its  effect  is  not  injurious.  There  may  be 
present  from  .09  gs.  in  100  gs.  in  light  white  wine  to  .14  gs.  in  a  heavy 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  419 

red  wine  without  deterioration   of   quality.     In   sweet   wines   even   a 
somewhat  larger  amount  may  be  present  without  causing  injury. 

Much  larger  amounts  are  injurious  in  two  ways.  When  the  acetic 
acid  is  perceptible  to  the  taste,  the  wine  is  spoiled.  "When  an  abnormal 
amount  of  acetic  acid  is  produced,  before  or  during  fermentation,  it 
interferes  with  or  stops  the  work  of  the  yeast.  In  such  cases,  the  wine 
"sticks,"  that  is,  fails  to  eliminate  all  sugar  and  becomes  especially 
liable  to  the  attacks  of  other  bacteria. 

Wines  high  in  alcohol  are  less  liable  to  acetic  fermentation  than 
weaker  wines.  Sound  wines  containing  ovjer  fourteen  per  cent  by 
volume  are  almost  immune,  but  such  wines  may  be  spoiled  during  the 
fermentation  by  the  growth  of  acetic  bacteria  on  the  exposed  floating 
"cap"  of  pomace  or  on  the  crushed  grapes,  especially  at  high  temper- 
atures. 

(6)  Anaerobic  Organisms. — Some  of  the  worst,  most  frequent  and 
most  difficult  to  treat  of  the  diseases  and  defects  of  wine  are  due  to 
organisms  which  develop  only  in  the  absence  of  oxygen.  These  organ- 
isms are  all  bacterial  and  appear  to  include  a  large  number  of  forms, 
though,  owing  to  difficulties  of  isolation  and  culture,  the  different  forms 
have  not  been  well  studied  or  described. 

1.  Slime-forming  Bacteria.  Musts  and  wines  become  slimy,  rarely, 
through  the  action  of  Dematium  pullulans  (Wortmann)  and  wild  yeasts 
(Meisner)  in  the  presence  of  oxygen ;  more  frequently  through  the  action 
of  special  bacteria.  In  most  cases,  only  young  wines  after  fermentation 
and  when  contained  in  closed  casks  or  bottles  exhibit  this  defect.  A 
slimy  wine  has  an  oily  appearance,  pours  without  splashing,  and,  in 
extreme  cases,  becomes  cloudy  and  will  hang  from  a  glass  rod  in  strings. 
In  such  wines,  the  microscope  reveals  large  numbers  of  spherical  or 
more  or  less  elongated  bacteria  in  long  chains. 

These  bacteria  attack  the  sugar,  but  not  the  glycerine  nor  the  alcohol, 
and  produce  mannite,  carbonic  acid,  lactic  and  acetic  acids  and  alcohol. 
Alcohol  above  thirteen  per  cent,  free  tartaric  acid,  tannin  and  sulfurous 
acid  in  small  amounts  prevent  their  growth.  The  disease  is  usually  not 
serious  and  disappears  under  the  ordinary  cellar  treatment. 

2.  Propionic  and  Lactic  Acid  Bacteria.  The  most  serious  and  per- 
haps the  commonest  disease  of  wines  is  characterized  by  persistent 
cloudiness,  disagreeable  odors  and  flavors,  increase  of  volatile  acid  and 
injury  to  or  complete  destruction  of  the  color.  Wines  affected  are 
characterized  commonly  as  mousey,  lactic  or  turned  wines  (Pousse  and 
Tourne  of  the  French). 

The  cause  is  bacteria.  These  are  readily  revealed  by  the  microscope 
in  enormous  numbers  in  badlv  affected  wines.     There  seem  to  be  several 


420  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION. 

or  many  closely  related  forms,  all  short  rod-shaped,  isolated  in  the  first 
stages  of  the  disease,  but,  later,  forming  chains  or  filaments  of  various 
lengths.  The  most  noticeable  changes  caused  in  the  composition  of  the 
wine  are  the  decrease  of  fixed  and  the  increase  of  volatile  acidity.  The 
tartaric  acid  and  tartrates  are  destroyed,  and  carbonic,  acetic,  lactic, 
propionic  and  other  volatile  acids  formed. 

Light  wines  of  low  acidity  are  most  subject  to  this  disease,  which  may 
be  prevented  by  measures  which  increase  the  acidity  and  alcohol, 
defecate*  and  attenuate  the  wine  rapidly  and  completely,  by  the  proper 
use  of  sulfurous  acid,  and  finally,  by  timely  nitration  and  pasteurization. 
Wines  noticeably  affected  can  be  used  only  for  distilling;  those  badly 
affected  are  valueless. 

3.  Mannitic  Bacteria.  Very  sweet  grapes  of  low  acidity  in  hot 
climates  are  subject  during  fermentation  to  a  similar  trouble  character- 
ized by  increase  of  volatile  acidity?  a  persistent  cloudiness  and  a  vapid 
sweet-sour  taste.  The  disease  is  commonly  confused  with  the  preced- 
ing but  is  caused  by  bacteria  of  different  forms.  The  form  described 
by  Gayon  is  a  very  fine  short  rod  which  does  not  unite  in  filaments. 
It  attacks  the  sugar,  especially  the  levulose,  producing  volatile  acids 
and  mannite.  The  latter  may  reach  over  two  per  cent  and  the  former 
five  per  cent,  giving  a  sweet-sour  wine  which  is  completely  spoiled. 

The  bacteria  grow  abundantly  only  at  high  temperatures,  approach- 
ing 104°  F.,  and  can  be  controlled  by  cool  fermentation,  increase  of 
acidity  and  proper  use  of  sulfurous  acid. 

4.  Butyric  Acid  Bacteria.  In  the  cooler  climates,  wines,  especially 
old  red  wines  in  bottles,  often  become  bitter.  This  trouble  is  due  to 
comparatively  large  rod-shaped  bacteria,  first  described  by  Pasteur. 
The  cells  remain  united  in  angular  filaments,  short  at  first,  but  becoming 
longer  and  finally  thicker,  by  incrustations  of  coloring  matter,  with  age. 

The  tannin,  coloring  matter,  and  glycerine  of  the  wine  are  attacked, 
acetic  and  butyric  acids  being  formed.  In  small  amounts  the  bacteria 
do  little  or  no  harm,  in  larger  amounts  they  may  spoil  the  wine.  Means 
which  increase  the  alcohol,  tannin  and  acidity  diminish  the  liablity  to 
the  disease.  Prompt  attenuation  and  clarification  and  in  extreme  cases, 
pasteurization,  will  cure  wines  not  too  badly  affected. 

All  the  above  anaerobic  bacteria  of  wine  diseases  probably  exist  in 
most  wines.  Which  develop  most  or  whether  any  develop  sufficiently 
to  injure  the  wine  depends  on  conditions,  chiefly  the  composition  of  the 
must  and  the  temperature  at  which  the  wine  is  fermented  or  stored. 
Mos1  <lis<';isc(l  wines  show  a  mixed  infection  of  several  forms. 


Bulletin  213]  THE  PRINCIPLES  OF   WINE-MAKING.  421 


VI.    CONTROL  OF  THE  MICRO-ORGANISMS. 

Given  grapes  of  suitable  composition,  the  quality  of  the  wine  depends 
on  the  work  of  the  micro-organisms.  The  art  of  the  wine-maker  consists 
almost  entirely  in  the  control  of  these  micro-organisms.  His  success  in 
facilitating  the  work  of  the  useful  form  (true  wine  yeast)  and  in  pre- 
venting or  hindering  that  of  injurious  forms  determines  the  quality 
of  his  product. 

(a)  Before  the  Fermentation. — On  the  skins  of  sound  ripe  grapes  as 
they  hang  in  the  vineyard,  the  micro-organisms  are  comparatively  few 
and  in  an  inactive  condition  and  with  intelligent  methods  they  can  not 
injure  the  wine.  On  broken  or  injured  grapes  the  number  is  greater  and 
the  forms  more  active.  If  many  such  grapes  occur  they  should  not  be 
mixed  with  the  sound  grapes  if  the  best  wine  is  to  be  made. 

1.  Gathering  the  Grapes.  The  sorting  of  grapes  after  gathering  is 
-  expensive  and  unsatisfactory.  The  best  method  for  the  separation  of 
inferior  grapes  is  by  "  double  picking. ' '  This  may  be  done  by  furnish- 
ing each  picker  with  two  boxes,  one  for  the  sound  grapes  and  the  other 
for  the  rest.  A  better  method,  however,  is  to  gather  only  the  good 
grapes  at  first.  If  many  inferior  grapes  are  left  it  may  be  profitable 
to  go  over  the  vineyard  a  second  time  for  these.  These  inferior  grapes 
can  then  be  made  up  separately  by  special  methods  and  by  such  means 
can  often  be  made  into  a  fair  wine,  and  at  worst  are  useful  as  distilling 
material.  If  the  grapes  left  are  too  few  to  repay  a  second  picking,  it 
is  better  to  leave  them  and  lose  them  completely  than  to  mix  them  with 
the  good  grapes  and  make  all  the  wine  inferior.  Any  bunches  which 
show  more  than  a  few  moldy,  cracked  or  diseased  berries  should  be  left. 
In  case  the  larger  part  of  the  crop  shows  defects  of  this  kind,  it  may  be 
best  to  gather  them  all  at  once  and  treat  them  as  inferior  grapes,  but 
in  this  case  fine  wine  can  not  be  made. 

Care  should  be  taken  to  avoid  unnecessary  bruising  of  the  fruit  if  it 
can  not  be  worked  immediately.  Molds,  wild  yeasts  and  vinegar  bacteria 
multiply  rapidly  on  grapes  wet  with  juice,  The  sooner  the  grapes  can 
be  crushed  and  placed  in  the  fermenting  vat  or  press  the  easier  it  is  to 
obtain  a  sound  fermentation. 

If  the  grapes  are  to  remain  for  two  or  more  days  after  they  are  gath- 
ered before  being  delivered  to  the  winery,  special  precautions  should  be 
taken.  Even  with  great  care  in  gathering,  handling  and  protecting 
from  dust  and  heat,  grapes  will  deteriorate  if  kept  more  than  two  days 
without  crushing.  If  bruised  and  hot  they  will  undergo  injurious 
changes  even  sooner. 


422  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

2.  Transportation  of  Grapes.  "When  grapes  have  to  be  taken  long 
distances  by  wagon  or  railroad  it  is  best  to  crush  them  at  the  vineyard, 
and  then  transport  them  in  tight  vats  or  tanks.  They  may  commence 
to  ferment  before  they  arrive  at  the  winery,  but  this  effect  of  the  wild 
yeasts  on  the  crushed  grapes  is  much  less  deleterious  than  that  of  the 
molds  and  vinegar  bacteria  on  the  uncrushed.  Fermentation  can  be 
delayed  and  minimized  by  crushing  the  grapes  as  cold  as  possible. 

The  coolness  of  the  grapes  can  be  insured  by  crushing  those  gathered 
in  the  morning  immediately  before  they  have  had  time  to  become  warm. 
Those  gathered  during  the  heat  of  the  day  can  be  cooled  by  leaving  them 
in  the  picking  boxes  distributed  along  the  avenues  all  night.  If  they 
are  not  piled  up  until  the  following  morning,  they  will  usually  cool  off 
fifteen  or  twenty  degrees  or  more.  They  may  then  be  crushed,  or,  if 
necessary,  piled  up.  Large  masses  of  grapes,  such  as  a  pile  of  full  boxes, 
cool  off  or  warm  up  slowly. 

The  best  method  of  preventing  injurious  fermentation,  however,  is  to 
distribute  a  carefully  measured  quantity  of  potassium  meta-bisulfite 
equally  through  each  receptacle  containing  the  crushed  grapes.  The 
quantity  needed  will  depend  on  the  temperature  and  condition  of  the 
grapes.  If  the  grapes  are  cool  and  sound,  from  5  oz.  to  6  oz.  for  each 
ton  will  be  sufficient,  if  warm  or  moldy,  9  oz.,  12  oz.  or  16  oz.  will  be 
necessary. 

The  sulfite  may  be  sprinkled  over  the  crushed  grapes  as  they  fall  into 
the  receiving  vat,  but  it  is  difficult  to  get  a  proper  distribution  in  this 
way.  It  is  better  to  dissolve  it  first  in  hot  water.  If  the  solution  is 
made  at  the  rate  of  one  pound  of  meta-bisulfite  to  one  gallon  of  water, 
it  is  easy  to  measure  the  calculated  amount.  A  good  way  to  use  it  is  to 
put  the  amount  needed  in  a  vessel  furnished  with  a  small  tap  and  to 
let  the  solution  drip  from  this  tap  into  the  vat,  or  better  into  the  crusher, 
as  the  grapes  are  passing  through. 

The  amount  of  sulfurous  acid  introduced  in  this  way  will  be  just  about 
what  is  needed  in  the  fermentation,  and  is  much  more  effective  and 
beneficial  if  added  at  this  time  than  later. 

3.  Cleanliness.  The  less  foreign  .matter  we  get  into  the  fermenting 
vat,  the  better  our  wine  will  be.  Grapes  as  they  hang  in  the  vineyard 
are  usually  clean  except  in  the  vicinity  of  dusty  roads  or  on  vines 
pruned  so  low  that  the  fruit  rests  on  the  soil.  Soil  and  dust,  however, 
are  more  or  less  eliminated  from  the  liquid  during  the  first  part  of  the 
processes  of  wine-making  and  are  much  less  harmful  than  molds  and 
bacteria. 

The  most  harmful  forms  of  dirt  are  those  to  which  grapes  may  be 
exposed  after  gathering.  Grapes  gathered  in  moldy,  vinegar-sour  boxes, 
hauled   iD   dirty  wagons  or  cars  and  passed  through   dirty  crushers, 


Bulletin  213]  the  principles  of  wine-making.  423 

conveyers  and  presses  may  be  so  completely  infected  with  injurious 
germs  that  it  is  impossible  to  obtain  a  good  fermentation.  The  most 
injurious  form  of  dirt  is  grapes,  must  or  wine  which  have  been  allowed 
to  become  moldy  or  vinegar-sour. 

Picking  boxes  or  other  receptacles  for  grapes  should  not  remain  more 
than  twenty-four  hours  after  using  without  washing.  "Where  this  is 
impossible,  they  should  be  exposed  to  the  sun  and  thoroughly  dried. 
Molds  will  not  grow  on  a  dry  surface  even  though  it  is  covered  with 
grape  juice.  The  same  treatment  is  necessary  for  crushers,  pumps, 
hoses  and  all  machinery  and  utensils  with  which  the  grapes  come  in 
contact.  Surfaces  which  can  not  be  dried  quickly,  such  as  the  inside 
of  closed  vats,  should  be  sterilized  with  the  fumes  of  burning  sulfur. 
This  sulfuring  is  not  necessary  in  the  case  of  metal  surfaces,  such  as 
the  interior  of  pumps  and  pipe  lines,  which  can  usually  be  kept  free  from 
mold  if  well  washed  and  drained  after  using.  All  pipe  lines  should  be 
furnished  with  drainage  cocks  at  all  low  points  and  pump  wells  should 
have  an  opening  at  the  bottom  so  that  they  can  be  washed  and  drained 
easily.  Hose  should  be  hung  up  vertically  when  not  in  use.  Picking 
boxes  should  be  thoroughly  dry  before  being  stacked  away  for  the 
winter,  or,  if  this  is  inconvenient,  they  should  be  stored  in  a  close  room 
and  sulfur ed  occasionally. 

4.  Defecation  of  Must.  However  carefully  the  grapes  are  handled, 
a  certain  amount  of  dust,  germs,  and  other  injurious  matters  will  reach 
the  vats  and  presses.  If  these  matters  are  left  in  the  must  during 
fermentation,  they  injure  the  delicacy  of  the  flavor  of  the  wine.  It  is 
desirable  in  the  manufacture  of  white  wines  to  have  a  clear  must  to 
ferment. 

The  clearing  of  the  must  can  be  accomplished  in  several  ways. 
Mechanical  separators  similar  in  principle  to  those  used  in  creameries 
are  sometimes  used,  but  the  clearing  is  not  sufficiently  complete.  Their 
main  use  is  to  separate  the  bulk  of  the  solid  matter  from  must  which 
has  been  extracted  by  a  continuous  press. 

Small  quantities  of  must  can  be  cleared  with  gelatinous  matters  and 
tannin  as  in  fining  wine.  Owing  to  the  higher  specific  gravity  of  must 
and  its  viscidity,  the  finings  often  settle  with  difficulty.  The  settling 
is  facilitated  by  the  addition  of  Spanish  clay  or  infusorial  earth,  but  the 
method  is  too  slow  and  uncertain  for  large  scale  practice. 

Most  musts  will  clear  sufficiently  in  twenty-four  to  forty-eight  hours 
by  simple  settling,  if  fermentation  can  be  delayed  so  long.  With  per- 
fectly sound  grapes  and  clean  vats  in  cold  weather,  no  other  treatment 
is  necessary.  As  soon  as  the  impurities  have  formed  a  sediment,  the 
clear  must  is  drawn  off  into  the  fermenting  vessels. 

3— b213 


424  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

As  a  rule,  fermentation  starts  before  the  settling  is  complete.  Soon 
after  the  commencement  of  the  vintage,  the  crushers  and  conveyors 
supply  an  abundance  of  yeast  to  the  must  and,  if  the  weather  is  hot,  it 
may  be  fermenting  before  it  gets  into  the  defecating  vat.  Even  in 
cases  where  there  is  no  perceptible  fermentation  during  the  first  twenty- 
four  hours  and  where  the  settling  is  satisfactory,  there  is  always,  unless 
the  grapes  are  very  cold,  a  multiplication  of  apiculate  and  other  wild 
yeasts.  It  is  nearly  always  advisable  to  treat  the  must  with  sufficient 
sulfurous  acid  to  delay  all  growth  of  micro-organisms  until  it  can  be 
decanted  from  the  sediment. 

If  the  grapes  have  been  treated  with  meta-bisulfite  before  or  during 
crushing,  this  will  suffice.  This  is,  indeed,  the  best  time  to  apply  the 
sulfurous  acid,  as  it  prevents  even  the  commencement  of  growth  of  unde- 
sirable organisms.  If  this  has  not  been  done,  the  sulfuring  may  be 
accomplished  by  pumping  the  must  into  a  closed  vat  in  which  sulfur  has 
been  burned. 

The  amount  of  sulfur  or  sulfite  to  use  will  depend  on  the  temperature 
and  on  the  nature  of  the  must.  The  higher  the  temperature  and  the 
more  contaminated  the  must  the  more  sulfurous  acid  is  necessary. 
From  12  to  16  oz.  of  meta-bisulfite  to  one  thousand  gallons  is  an  average 
amount.  The  amount  of  sulfurous  acid  which  gets  into  the  must  from 
the  fumes  of  burning  sulfur  depends  so  much  on  the  size  of  the  cask,  the 
method  of  filling  and  other  conditions  that  no  definite  amount  can  be 
stated.  Where  every  precaution  is  taken  to  make  the  must  absorb 
nearly  all  the  fumes,  4  oz.  to  5  oz.  of  sulfur  to  a  thousand  gallons  is 
sufficient.  Where  the  sulfur  is  simply  burnt  in  the  cask  and  the  wine 
pumped  in,  somewhat  more  is  needed.  If  the  must  commences  to 
ferment  before  it  clears,  more  sulfur  should  be  used  the  next  time.  If 
it  remains  without  fermenting  for  several  days  after  adding  yeast,  less 
should  be  used. 

No  harm  need  be  anticipated  from  a  slight  excess  of  sulfurous  acid 
at  this  time.  A  large  part  of  it  escapes  into  the  air  before  and  during* 
fermentation  and  the  remainder  forms  combinations  with  the  sugar  and 
other  components  of  the  must  which  are  tasteless  and  innocuous. 

An  exception  should  be  made  perhaps  of  very  acid  musts.  Sulfurous 
acid  tends  to  preserve  the  normal  fixed  acidity  of  the  must.  Wine  made 
from  unsulfured  must  has  a  lower  fixed  acidity  than  the  must.  The 
acidity  of  wine  made  from  sulfured  must  is  nearly  or  quite  equal  to 
that  of  the  must.  For  this  reason  sulfiting  is  especially  beneficial  in  the 
case  of  musts  of  low  acidity.  For  unduly  acid  musts  or  in  the  manu- 
facture of  sweet  wines  where  a  low  acidity  is  desirable,  it  may  be  objec- 
tionable. 

The  cause  of  the  preservation  of  acidity  is  probably  the  prevention 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKING.  425 

of  the  growth  of  acid  consuming  micro-organisms,  such  as  the  apiculate 
yeast. 

In  from  twelve  to  twenty-four  hours,  the  must  is  purged  of  all  its 
gross  impurities,  including  micro-organisms,  dust  and  solid  particles 
derived  from  the  skins,  stems,  pulp,  and  leaves.  It  may  be  slightly 
cloudy  or  nearly  clear.  It  should  then  be  drawn  off  into  clean  casks 
and  fermentation  started  with  yeast. 

This  defecation  is  of  great  value,  ridding  the  must  of  substances  that 
would  affect  the  flavor  of  the  wine  in  the  heat  of  fermentation  and 
eliminating  the  excess  of  albuminoid  matters  that  would  serve  as  food 
for  injurious  bacteria.  "Wine-makers  who  use  it  for  the  first  time  are 
usually  surprised  at  the  great  improvement  in  the  quality  of  the  wine 
and  in  the  ease  with  which  it  can  be  handled. 

5.  Sterilization.  The  defecation  of  must  for  white  wine,  as  just 
described,  eliminates  nearly  all  the  non-living  solid  matters  but  leaves 
more  or  less  of  the  micro-organisms.  Many  attempts  have  been  made 
to  devise  a  method  of  sterilization  that  would  remove  or  destroy  all  the 
micro-organisms.  This  can  be  accomplished  by  heating,  but  the  results 
are  not  satisfactory.  High  heating  caramelizes  part  of  the  sugar  and 
oxidizes  the  'must,  injuring  the  flavor  and  color  of  the  resulting  wine. 
Several  successive  heatings  at  a  lower  temperature  in  an  atmosphere  of 
carbonic  acid  gas  is  preferable  but  troublesome  and  costly.  Both 
methods  have  the  defect  of  extracting  undesirable  substances  from  the 
solid  matters  contained  in  the  must  unless  they  are  previously  removed 
by  defecation. 

Chemical  sterilization  by  means  of  disinfectants  is  still  less  practicable. 
No  substance  could  be  used  for  this  purpose  except  sulfurous  acid  and 
this  used  in  sufficient  quantities  would  injure  the  flavor  of  the  wine. 
The  effect  would  be  totally  different  from  that  of  the  small  quantities 
used  in  defecation. 

Experience  has  shown  that  the  absolute  sterilization  of  the  must  or 
grapes  is  quite  unnecessary.  Proper  defecation  of  the  must  removes 
a  large  proportion  of  the  undesirable  micro-organisms  and  what  remain 
have  no  opportunity  to  injure  the  wine  if  the  yeast  fermentation  is 
prompt  and  properly  conducted.  In  the  manufacture  of  red  wine, 
where  preliminary  defecation  is  impossible,  care,  cleanliness  and  prompt 
fermentation  are  usually  sufficient  to  prevent  any  serious  injury  and 
when  properly  supplemented  by  accurate  use  of  meta-bisulfite,  enable 
us  to  prevent  injurious  action  in  all  cases. 

6.  Starters.  All  the  methods  discussed  have  for  their  object  the 
diminution  or  elimination  of  micro-organisms  of  all  kinds.  With  the 
injurious  forms  the  true  yeast  is  also  removed.  The  more  perfect  these 
methods,  the  more  necessary  it  is  to  add  wine  yeast.     Without  this  addi- 


426  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

tion,  in  fact,  all  these  precautions  may  result  in  harm,  for  the  wine- 
yeast  being  present  in  much  smaller  numbers  than  many  of  the  injurious 
forms  may  be  completely  removed  while  enough  of  other  forms  is  left 
to  spoil  the  wine. 

A  "starter"  of  some  kind  is  therefore  necessary  with  defecated  must 
and  useful  in  all  other  cases. 

One  method  of  producing  such  a  starter  is  to  gather  a  suitable  quan- 
tity of  the  cleanest  and  soundest  ripe  grapes  in  the  vineyard,  crush 
them  carefully  and  allow  them  to  undergo  spontaneous  fermentation 
in  a  warm  place.  An  addition  of  a  quarter  to  a  third  of  an  ounce  of 
potassium  meta-bisulfite  to  one  hundred  pounds  of  grapes  will  be  of 
great  assistance  in  promoting  a  good  yeast  fermentation  in  the  starter. 
Perfectly  ripe  grapes  should  be  selected  and  the  fermentation  allowed 
to  proceed  until  at  least  10  per  cent  of  alcohol  is  produced.  If  imper- 
fectly ripe  grapes  are  used  or  the  starter  used  too  soon,  the  principal 
yeast  present  may  be  apiculatus.  Towards  the  end  of  the  fermentation 
ellipsoideus  predominates.  From  one  to  three  gallons  of  this  starter 
should  be  used  for  each  hundred  gallons  of  grapes  or  must  to  be 
fermented.  Too  much  should  not  be  used  in  hot  weather  or  with  warm 
grapes,  or  it  may  be  impossible  to  control  the  temperature. 

This  starter  is  used  only  for  the  first  vat  or  cask.  Those  following 
are  started  from  previous  fermentations,  care  being  taken  always  to  use 
the  must  only  from  a  vat  at  the  proper  stage  of  fermentation  and  to 
avoid  all  vats  that  show  any  defect. 

7.  Pure  Yeast.  An  improvement  on  a  natural  starter  of  this  kind  is 
a  pure  culture  of  tested  yeast.  Such  yeasts  are  used  extensively  in 
Germany  and  France  and  have  been  employed  in  several  Californian 
wineries  for  some  years  with  excellent  results. 

There  are  two  ways  of  using  these  yeasts.  One  is  to  obtain  from  a 
pure  yeast  laboratory  a  separate  starter  for  each  fermenting  vat  or  cask. 
All  the  wine-maker  has  to  do  is  to  distribute  this  starter  in  the  grapes 
or  must  as  they  run  into  the  vat.  If  the  starter  is  used  when  in  full 
vigor  this  method  is  simple  and  effective.  Unfortunately,  it  is  difficult 
to  have  it  on  hand  in  just  the  right  condition  at  the  right  moment.  If 
the  starter  is  too  young  it  will  not  contain  enough  yeast  cells,  if  too  old 
the  cells  will  be  inactive  or  dead.  The  usual  starter  is  in  full  vigor 
for  only  a  few  days  at  the  most.  Recent  improvements  in  the  methods 
of  preparing  pure  yeast  starters  are  said  to  overcome  this  difficulty  and 
to  produce  starters  which  maintain  their  full  vigor  for  weeks  or  months. 

The  other  method  is  for  the  wine-maker  to  obtain  a  small  culture  of 
pure  yeast  from  a  reliable  source  and  from  this  to  make  his  own  starter. 

To  do  this  he  prepares  two  or  three  gallons  of  must  defecated  with 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  427 

sulfurous  acid  and  sterilized  by  boiling.  This,  on  cooling,  is  placed 
in  a  large  demijohn  plugged  with  sterilized  cotton  and  the  pure  culture 
of  yeast  added.  The  demijohn  must  be  placed  in  a  warm  place  (70° 
to  80°  F.)  and  thoroughly  shaken  several  times  a  day  to  aerate  the 
must.     In  a  few  days  a  vigorous  fermentation  occurs. 

When  the  fermentation  is  at  its  height  in  the  demijohn,  which  will  be 
when  the  must  still  contains  3  or  4  per  cent  of  sugar,  it  is  ready  to  use 
to  prepare  a  starter.  This  is  best  prepared  in  a  small  open  vat  or  tub, 
varying  in  size  according  to  the  amount  of  starter  needed  daily.  In 
this  tub  is  poured  twenty  to  fifty  gallons  of  well  defecated  must 
extracted  from  clean  sound  grapes.  It  is  not  necessary  to  boil  it,  as  the 
few  micro-organisms  it  may  contain  will  be  without  effect  in  the  pres- 
ence of  the  vastly  more  numerous  yeast  cells  introduced  from  the  pure 
culture  in  the  demijohn. 

The  whole  of  the  pure  culture  is  poured  into  the  tub  of  must,  the 
temperature  of  which4  should  be  between  80°  and  90°  F.  This  temper- 
ature is  maintained  either  by  warming  the  room  or  by  occasionally 
placing  a  large  can  full  of  boiling  water  in  the  tub.  This  can  should,  of 
course,  be  tightly  stoppered  in  order  that  none  of  the  water  may  get  into 
the  must.  The  must  should  be  well  aerated  several  times  a  day  to 
invigorate  the  yeast.  This  is  done  by  dipping  out  some  of  the  must  with 
a  bucket  or  ladle  and  pouring  it  back  into  the  tub  from  a  height  of 
several  feet  or  by  the  use  of  compressed  air.  The  tub  should  be  covered 
with  a  cloth  to  exclude  dust,  and  everything  with  which  the  must  comes 
in  contact  should  be  thoroughly  cleaned  with  boiling  water. 

In  a  day  or  two  the  must  is  in  full  fermentation  and  may  be  used  as 
a  starter.  From  ten  to  thirty  gallons  of  starter  are  used  for  every 
thousand  gallons  of  must  or  crushed  grapes.  The  cooler  the  grapes 
the  more  should  be  added.  Too  much  added  to  warm  grapes  may  make 
the  fermentation  so  rapid  that  it  will  be  difficult  to  control  the  temper- 
ature. Moldy  or  dirty  grapes  require  more  than  clean,  because  there 
are  more  injurious  germs  to  overcome. 

Every  twenty-four  hours,  nine  tenths  of  the  contents  of  the  starter 
tub  can  be  used  and  immediately  replaced  with  fresh  defecated  must. 
The  yeast  in  the  one  tenth  remaining  is  sufficient  to  start  a  vigorous 
fermentation  and  multiplication  of  yeast.  Two  things  must  be  watched 
with  special  care  if  the  starter  is  to  maintain  it  vigor.  The  temperature 
must  be  kept  above  80°  F.  and  thorough  and  frequent  aeration  must  be 
given. 

With  care,  a  starter  of  this  kind  will  remain  sufficiently  pure  to  be 
used  continuously  throughout  the  vintage. 

(6)  During  the  Fermentation.  However  carefully  we  have  excluded 
injurious  germs  and  increased  the  good  yeast,  fermentation  will  not  be 


428  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

successful  unless  we  maintain  conditions  as  favorable  to  the  latter  and 
as  unfavorable  to  the  former  as  possible. 

1.  Starting  Temperature.  The  temperature  of  the  crushed  grapes 
or  expressed  must  is  of  importance.  If  it  is  below  60°  F.,  unless  the 
weather  is  warm,  they  should  be  warmed  to  70°  or  75°  F.  Unless  this 
is  done,  the  molds  and  apiculatus,  which  require  less  heat  than  ellip- 
soideus  will  develop  more  quickly.  This  is  especially  true  when  starters 
are  not  used.  In  the  warmer  and  earlier  districts  the  grapes  are 
practically  never  too  cold.  On  the  other  hand,  unless  there  is  great 
carelessness,  they  are  never  too  hot  for  the  commencement  of  fermenta- 
tion. The  hotter  they  are,  however,  the  more  artificial  cooling  will  be 
necessary  later  and  the  sooner  it  will  have  to  commence. 

2.  Crushing.  Thorough  crushing  is  necessary  in  the  case  of  white 
wine,  to  facilitate  the  expression  of  the  juice.  For  red  wine,  the  grapes 
are  crushed,  and  skin,  pulp  and  juice  fermented  together.  In  this  case 
also,  thorough  crushing  is  necessary.  Imperfectly  crushed  grapes 
ferment  unevenly  and  incompletely  and  the  growth  of  mold  is  much 
facilitated.  Crushing  of  the  seeds  should  be  avoided  or  the  quality  and 
clearness  of  the  wine  will  be  injured. 

3.  Aeration.  The  must  should  be  thoroughly  saturated  with  air  at 
the  beginning  of  fermentation  to  insure  the  multiplication  of  the  yeast. 
The  aeration  received  in  the  processes  of  stemming,  crushing  and  press- 
ing is  usually  sufficient  for  this  purpose.  More  aeration  would  be  harm- 
ful, injuring  the  flavor  and  color  of  the  wine  by  over  oxidation  and 
promoting  the  growth  of  injurious  aerobic  organisms.  An  objection 
to  the  sterilization  of  must  by  heat  is  the  expulsion  of  the  air  and  the 
difficulty  of  replacing  it  in  the  proper  amount. 

4.  Use  of  Sulfurous  Acid.  The  proper  use  of  sulfurous  acid  in  the 
regulation  of  fermentation  is  one  of  the  most  important  and  necessary 
but  least  understood  parts  of  the  wine-maker's  art.  Only  by  this 
proper  use  in  most  cases  can  wholesome  wine  of  the  highest  quality  be 
produced.  Improper  use  will  injure  or  completely  spoil  the  wine.  Its 
beneficial  effects  are  due  primarily  to  its  action  on  micro-organisms,  on 
enzymes  and  on  the  color  of  the  wine. 

In  the  small  quantities  properly  used  in  wine-making,  it  is  antiseptic 
in  a  degree  varyiDg  with  the  amount.  All  micro-organisms  are  sus- 
eeptible  to  its  action  in  varying  degrees.  Bacteria  are  particularly 
sensitive,  molds  and  pseudo-yeasts  less  so,  while  wine  yeast  is  the  most 
resistant  of  the  ordinary  forms  found  in  must  and  wine. 

The  result  of  the  use  of  the  proper  amount  in  crushed  grapes  and 
must  before  fermentation  is  the  almost  complete  suppression  of  bacterial 
action,  the  discouragement  of  molds  and  pseudo-yeasts  and  the  promo- 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  429 

tion  of  the  growth  of  wine  yeast  which  is  given  a  clear  field  unhindered 
by  the  deleterious  excretions  of  its  competitors. 

Its  action  as  regards  enzymes  is  hardly  less  important.  It  would  be 
impossible  to  make  the  finest  wines  of  Sauternes  and  the  Rheingau 
without  its  use  on  account  of  the  oxydase  produced  by  the  Botrytis 
cinerea  which  is  abundant  and  necessary  on  the  best  grapes  of  these 
regions.  In  other  regions  where  this  mold  and  others  occasionally  occur, 
its  use  is  also  necessary.  In  hot  climates,  it  is  especially  useful,  not  only 
because  bacterial  action  is  more  intense  in  such  regions,  but  because  of 
its  action  in  preserving  the  natural  fixed  acids  of  the  grapes,  which  are, 
there,  nearly  always  deficient.  This  preservation,  according  to  Wort- 
mann,  is  due  to  the  suppression  of  acid-consuming  bacteria,  but  experi- 
ments of  Astruc  tend  to  show  that  the  prevention  of  the  action  of 
unknown  acid-destroying  enzymes  is  in  part  the  cause. 

Its  action  on  the  color  of  wines  is  also  of  importance.  By  the  action 
of  oxygen,  the  color  of  red  wine  is  gradually  made  yellowish  and  finally 
rendered  insoluble  and  precipitated.  This  action  is  to  a  great  extent 
prevented  or  much  retarded  by  the  use  of  minute  quantities  of  sulfurous 
acid.  Wines  made  without  sulfuring  and  kept  in  casks  in  the  ordinary 
way  will  lose  from  one  third  to  two  thirds  of  their  color  during  the  first 
six  months.  This  loss  of  color  continues  until  finally  such  wines  as  port, 
after  keeping  for  many  years,  may  be  completely  deprived  of  all  their 
red  color  and  become  yellowish  or  brown. 

If  we  sulfur  a  red  wine  as  soon  as  it  is  taken  from  the  fermenting  vat, 
the  first  effect  is  to  diminish  its  color,  more  or  less  according  to  the 
amount  of  sulfur  used.  This  loss,  however,  is  not  all  permanent,  for 
after  the  first  racking  some  of  it  returns,  so  that  after  one  month,  the 
color  may  be  actually  deeper  than  immediately  after  the  first  sulfuring. 
The  color  remaining,  moreover,  is  more  stable  and  a  sulfured  wine  after 
six  months  may  have  fifty  per  cent  more  color  than  if  it  had  not  been 
sulfured.  The  color,  moreover,  will  be  of  a  better  tint.  If  the  sulfur- 
ing or  sulfiting  is  done  before  fermentation,  the  beneficial  effect  is  even 
more  striking.  In  this  case,  the  color  is  not  only  rendered  more  stable, 
but  the  sulfurous  acid  seems  to  cause  a  more  thorough  extraction  of  the 
color  so  that  the  wine  from  a  sulfited  vat  is  actually  darker  at  drawing 
off  than  that  from  one  where  no  sulfite  has  been  used. 

The  beneficial  effects  of  sulfurous  acid  on  the  color  of  white  wine  is 
equally  striking.  The  greenish  golden  color  of  white  wine  gradually 
changes  to  yellow  or  brown  with  age  and  oxidation.  This  undesirable 
change  is  much  diminished  by  a  proper  use  of  minute  quantities  of 
sulfurous  acid. 

The  most  commonly  used  source  of  sulfurous  acid  is  the  fumes  of 
burning  sulfur.     Sulfur  is  burned  in  a  cask  and  the  must  caused  to  take 


430  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

up  the  fumes  by  being  pumped  into  the  cask  through  the  upper  bung 
hole.  It  is  almost  impracticable  to  apply  sulfurous  acid  from  this 
source  to  crushed  grapes  for  red  wine. 

The  method  is  defective  in  many  ways.  It  is  impossible  to  tell  within 
very  wide  limits  how  much  sulfurous  acid  has  been  absorbed  by  the  wine. 
Moreover,  the  sulfur  burns  incompletely  and  the  volatilized  sulfur  acted 
upon  by  the  yeast  may  produce  sulfur etted  hydrogen.  Other  sulfur 
compounds  are  also  produced  during  the  burning,  to  some  of  which  the 
so-called  sulfur  taste  of  wine  is  said  to  be  due.  Several  devices  have 
been  invented  to  decrease  these  defects,  but  none  remove  them  com- 
pletely, and  progressive  wine-makers  are  adopting  more  reliable  sources. 

An  improvement  is  the  use  of  potassium  meta-bisulfite  K2S205,  a 
salt  which  can  be  obtained  in  the  requisite  purity  in  commerce  and 
which  contains  about  fifty  per  cent  by  weight  of  S02.  The  amount  of 
potash  added  by  this  salt  in  the  doses  used,  is  very  small  and  far  within 
the  limits  of  variation  between  different  wines.  By  the  use  of  this  salt, 
exact  amounts  of  sulfurous  acid  can  be  applied  both  to  white  and  red 
wines.     Other  sulfites  are  not  permissible. 

The  best  source  of  the  acid,  recently  brought  into  limited  use,  is  the 
liquified  gas.  This  can  be  manufactured  comparatively  cheaply  in 
great  purity.  By  its  use,  all  the  benefits  of  sulfurous  acid  are  obtained 
and  the  defects  eliminated. 

The  amount  of  potassium  meta-bisulfite  to  use  will  depend  on  the 
cemperature  and  on  the  condition  and  nature  of  the  grapes.  In  cold 
weather  and  with  cold  grapes  very  little  should  be  used  or  it  may  be 
difficult  to  start  fermentation.  With  very  acid  grapes,  less  is  needed,  as 
they  are  less  liable  to  bacterial  fermentation  and  the  preservation  of 
the  fixed  acids  due  to  the  sulfite  may  be  a  disadvantage.  In  making 
sweet  wines,  little  or  no  sulfite  should  be  used  as  most  of  them  are 
benefited  by  thorough  oxidation.  In  hot  weather  and  with  grapes  of 
low  acidity,  more  should  be  used,  especially  if  they  are  in  bad  condition, 
moldy  or  broken. 

The  amounts  which  have  been  found  to  give  the  best  results  are  from 
3  to  5  ounces  per  ton  in  cold  weather,  from  6  to  8  ounces  in  average 
conditions  and  from  10  to  12  ounces  in  hot  weather  or  for  moldy  grapes. 
"With  liquid  sulfurous  acid  half  these  quantities  are  sufficient.  The 
sulfite  should  be  thoroughly  distributed  throughout  the  vat,  if  neces- 
sary, by  pumping  over  until  the  outflowing  must  shows  by  its  brownish 
color  that  it  has  all' been  acted  on. 

The  addition  of  the  starter  should  be  made  within  two  or  three  hours 
after  the  sulfiting  and  the  yeast  distributed  evenly  throughout  the  vat 
in  the  same  way. 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  431 

5.  Increase  of  Acidity.  Some  grapes,  owing  to  their  composition, 
especially  their  high  acidity,  are  very  resistant  to  the  attacks  of 
injurious  bacteria.  Others,  owing  to  their  low  acidity  or  highly  nitrog- 
enous nature,  are  very  susceptible.  The  addition  of  tartaric  or  citric 
acid  to  the  latter  has  a  deterring  effect  on  some  of  the  most  dangerous 
forms.  It  is  seldom  necessary,  however,  to  modify  the  composition  for 
this  purpose  if  the  other  means  of  control  are  used.  The  addition  of 
acid  or  its  decrease  by  dilution  should  be  solely  for  the  direct  improve- 
ment of  the  taste. 

In  the  hotter  parts  of  California,  many  varieties  of  grapes  are  defi- 
cient in  natural  acidity  when  they  are  sufficiently  ripe  for  wine-making. 
This  defect  may  be  remedied  in  various  ways.  The  best  is  by  blending 
them  with  acid  grapes  of  other  varieties  or  other  localities  before 
fermentation,  whereby  the  wine  of  both  is  improved.  The  blending  of 
wines  too  high  with  wines  too  low  in  acidity,  after  fermentation,  is  also 
good  practice. 

Where  acid  grapes  are  unobtainable,  a  small  proportion  of  imperfectly 
ripe  second  crop  bunches  may  be  used  with  advantage.  If  only  a 
small  proportion  is  used,  the  wine  does  not  show  the  harshness  of  wines 
made  altogether  from  imperfectly  ripe  grapes. 

The  use  of  ' '  plaster ' '  or  gypsum  on  the  crushed  grapes  was  formerly 
very  common  for  this  purpose  but  is  not  advisable.  The  resulting  wine 
is  harsh  and  may  show  more  sulfate  than  is  allowed  by  certain  pure 
food  laws.  Phosphoric  acid  in  various  forms  has  been  used  for  the  same 
purpose  and  is  less  objectionable.  Its  main  object,  however,  the  promot- 
ing of  a  clean  fermentation,  is  more  effectually  accomplished  by  sul- 
furous  acid. 

"Where  it  is  considered  desirable  to  increase  the  acidity  of  a  wine  after 
making,  it  may  be  done  by  adding  tartaric  or  citric  acid.  The  former 
is  apt  to  produce  a  harsh  acidity  and  some  of  that  added  is  thrown 
down  as  cream  of  tartar.  Pure  citric  acid  is  preferable,  giving  a 
cleaner  and  more  agreeable  acidity  and  all  remaining  in  the  wine.  The 
amount  to  add  is  determined  by  taste,  but  in  any  case,  should  not  exceed 
one  and  a  half  pounds  per  100  gallons  of  wine. 

In  some  cases  an  addition  of  tannin  to  the  grapes  or  must  before 
fermentation  is  advisable.  In  making  white  wine  it  may  be  employed 
in  addition  to  or  instead  of  sulfurous  acid  for  the  preliminary  defeca- 
tion of  the  must.  It  coagulates  the  albuminoids  and  promotes  clearing. 
It  is  especially  useful  in  the  cooler  regions,  and  with  varieties  of  which 
the  must  is  rich  in  coagulable  albuminoids,  which  make  the  clearing  of 
the  wine  difficult.  From  one  half  to  two  thirds  of  an  ounce  may  be  used 
in  one  hundred  gallons  of  must  for  white  wine. 

It  may  be  used  in  a  similar  way  in  the  manufacture  of  red  wine,  and 
has  a  favorable  effect  on  the  color,  which  it  intensifies  and  renders  more 


432  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

stable.  It  is  especially  useful  for  grapes  which  have  been  badly  attacked 
with  molds.  From  eight  to  ten  ounces  may  be  used  to  a  ton  of  crushed 
grapes  or  nearly  twice  this  amount  in  the  case  of  moldy  grapes. 

Only  clean  tasting  tannin  extracted  by  water  and  alcohol  should  be 
used.  Ether-extracted  tannins  are  very  pure  and  white,  but  give  a 
persistent  taste  of  ether  to  the  wine.  New  oak  barrels  and  casks,  even 
after  thorough  cleaning  and  steaming,  yield  notable  amounts  of  tannin 
to  the  wine  which  is  often  benefited  thereby. 

The  tannin  is  obtained  in  the  form  of  a  light  powder  which  may  be 
sprinkled  on  the  crushed  grapes  or  preferably  dissolved  first  in  a  little 
warm  water  or  wine. 

6.  Modification  of  Sugar  Contents.  If  there  is  too  much  sugar  in 
the  grapes  the  yeast  can  not  eliminate  it  all  and  the  wine  will  remain 
sweet.  In  practice,  any  must  which  shows  more  than  25°  Bal.  is  very 
liable  to  remain  sweet.  Too  much  sugar  can  often  be  reduced,  like  too 
little  acid,  by  blending  with  under-ripe  grapes  and  both  defects  remedied 
at  the  same  time.  Where  this  is  impracticable  the  only  way  of  making 
dry  wine  from  over-sweet  grapes  is  to  reduce  the  sugar  by  the  addition 
of  water.  This  reduction  should  seldom  exceed  2  per  cent,  that  is  to 
say,  the  maximum  amount  of  water  that  may  be  added  is  about  fifteen 
gallons  to  the  ton  of  grapes.  Where  this  amount  is  not  sufficient  to 
reduce  the  sugar  to  a  point  where  it  can  be  all  eliminated  by  the  yeast, 
the  grapes  should  be  used  for  sweet  wine. 

When  the  sugar  is  too  abundant,  most  of  the  other  useful  components 
of  the  grapes  are  also  in  excess,  so  that  moderate  dilution  in  such  cases 
results  in  a  wine  of  normal  composition.  The  acidity,  however,  is  an 
exception.  High  sugar  is  nearly  always  accompanied  by  low  acidity. 
Dilution  with  water  must,  therefore,  nearly  always  be  accompanied  by 
addition  of  acid.  The  water  should  be  added  before  fermentation,  and 
the  acid  after,  where  sulfites  are  used. 

Increasing  the  sweetness  of  the  grapes  by  the  addition  of  pure  sugar 
is  allowed  and  practised  in  some  countries  but  is  practically  never  neces- 
sary in  California.  In  France,  the  law  allows  a  maximum  addition  of 
about  3  per  cent  by  weight  of  sugar.  In  the  United  States,  when  sugar 
is  added,  the  wine  must  be  sold  as  ' '  modified,  ameliorated,  or  corrected 
wine. ' '  The  addition  of  both  sugar  and  water  constitute  ' '  stretching, ' ' 
and  is  practised  only  in  the  manufacture  of  inferior,  imitation  wines. 

7.  Temperature  of  Fermentation.  The  quality  and  character  of  the 
wine  depend  greatly  on  the  temperature  of  the  fermentation.  If  too 
low,  it  may  be  unduly  prolonged,  the  wine-yeast  may  have  difficulty  in 
overcoming  its  competitors  and  the  wines  may  remain  inferior  and 
cloudy.  With  red  wine,  the  desired  color,  tannin  and  body  may  not  be 
ex1  racted.     On  the  other  hand,  if  the  temperature  is  too  high  the  results 


Bulletin  213]  the  PRINCIPLES  OF  WINE-MAKING.  433 

are  worse.  The  growth  of  bacteria  is  promoted,  injuring  the  wine  by 
the  volatile  acid  and  displeasing  flavors  produced  and  preventing  the 
proper  action  of  the  yeast.  Such  wines  may  remain  sweet  on  account 
of  the  failure  of  the  yeast  to  do  its  work-  and  become  unpleasantly  sour 
owing  to  the  volatile  acids  produced  by  the  bacteria. 

Some  means  of  controlling  the  temperature  is  therefore  always  needed. 
Where  heat  is  deficient,  it  may  be  supplied  by  direct  heating  of  the  must 
or  part  of  it,  or  by  heating  the  cellar.  Where  heat  is  excessive,  it  may 
be  diminished  by  crushing  only  cold  grapes,  using  small  fermenting 
vats  and  open  wineries  to  promote  radiation,  and  finally,  by  the  use  of 
cooling  machines  applied  directly  to  the  fermenting  wine. 

The  best  temperature  for  fermentation  depends  on  the  kind  of  wine. 
For  light  white  wines,  the  maximum  should  not  exceed  75°  or  80°  F. ; 
for  heavier  wines,  85°  or  90°  F.,  while  for  heavy  red  wines,  where  high 
extract  and  tannin  are  required,  it  may  be  allowed  to  reach  95°  F. 
Sound  wines  can  be  made  at  all  these  temperatures. 

8.  Aeration  During  Fermentation.  As  already  explained,  the  ordi- 
nary processes  of  treatment  of  grapes  result  in  sufficient  aeration  for 
the  multiplication  of  the  yeast.  With  grapes  containing  little  sugar, 
this  may  suffice  to  complete  fermentation.  With  sweeter  grapes,  the 
fermentation  usually  slackens  when  the  alcohol  reaches  11  or  12  per 
cent  by  volume  or  sooner,  unless  some  supplementary  aeration  is  given. 
With  white  wine,  this  is  seldom  done,  with  the  result  that  the  time  of 
fermentation  is  prolonged.  With  red  wine,  the  necessary  stirring  of  the 
pomace  to  promote  color  extraction  or  the  pumping  over  of  the  must 
in  the  cooling  process  usually  gives  a  large  amount  of  aeration  which 
is  sometimes  excessive.  Too  much  aeration  results  in  too  rapid  fer- 
mentation and  consequent  difficulty  in  controlling  the  temperature. 
It  may  also  have  a  deleterious  effect  on  the  color,  especially  if  S02  has 
not  been  used. 

In  any  case,  the  main  part  of  the  fermentation  should  be  over  in 
from  three  to  five  days  in  the  case  of  red  and  in  from  seven  to  fourteen 
days  in  the  case  of  white  wine.  With  heavy  musts,  however,  there  will 
still  remain  from  .5  to  1  or  2  per  cent  of  sugar.  With  certain  special 
wines  such  as  Sauternes  it  is  desirable  to  retain  the  slight  sweetness  due 
to  this  small  amount  of  unfermented  sugar.  This  is  accomplished  by 
the  judicious  use  of  sulfurous  acid,  prompt  clarification  by  filtration 
or  fining  and  when  necessary  by  pasteurization.  The  pasteurization 
tends  to  remove  those  albuminoids  which  are  coagulated  by  heat  and 
which  are  preferred  food  of  bacteria. 

9.  Completion  of  the  Fermentation.  In  the  case  of  dry  wines,  pro- 
tection from  bacteria  is  best  obtained  by  prompt  and  complete  attenua- 
tion.    Fermentation  should  not  be  allowed  to  cease  until  all  the  sugar 


434  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

has  disappeared.  For  this  purpose,  one,  two  or  more  aerations  by 
pumping  over  are  usually  necessary  immediately  after  the  end  of  the 
tumultuous  fermentation.  The  temperature  of  the  wine  should  not  be 
allowed  to  fall  sufficiently  to  check  the  action  of  the  yeast  until  all  the 
sugar  has  disappeared. 

Racking  into  small  casks  or  into  a  cool  cellar  before  the  wine  is  com- 
pletely dry  is  therefore  to  be  avoided. 

The  time  for  drawing  off  red  wine  from  the  pomace  in  the  fermenting 
vat  is  determined  by  the  amount  of  extraction  desired.  As  soon  as  the 
wine  has  extracted  as  much  color  and  tannin  from  the  skins  as  is 
required,  it  should  be  drawn  off  and  the  pomace  pressed.  The  amount 
of  sugar  remaining,  or  the  degree  of  "dryness,"  should  not  be  consid- 
ered. Fermentation  will  continue  just  as  well  in  the  storage  casks  with- 
out the  pomace  as  in  the  vats,  providing  the  wine  is  not  unduly  chilled 
in  the  transfer.  In  fact,  the  transfer  from  open  vats  in  an  open  ferment- 
ing room  to  closed  casks  in  a  closed  cellar  is  one  of  the  best  means  of 
maintaining  the  temperature  of  the  wine  during  the  last  stages  of  fer- 
mentation. 

The  drawing  off  and  pressing  give  an  aeration  which  invigorates  the 
yeast  and  helps  it  to  finish  its  work.  The  wine  in  casks  should  be  closely 
watched,  and,  if  not  perfectly  dry,  in  a  few  days  it  should  be  aerated 
by  pumping  over. 

The  yeast  should  be  retained  in  the  wine  until  its  action  on  the  sugar 
is  complete.  During  the  violent  fermentation,  the  yeast  is  kept  sus- 
pended in  the  body  of  the  liquid  by  the  rise  of  gas  bubbles.  In  the  slow 
after  fermentation,  the  main  bulk  of  the  yeast  sinks  and  forms  a  layer 
at  the  bottom,  where,  however,  it  continues  to  work.  If  the  wine  is 
racked  from  this  yeast  sediment  before  it  is  dry,  it  will  very  frequently 
cease  fermentation  and  remain  sweet.  This  is  a  very  dangerous  condi- 
tion for  the  wine.  New  yeast  often  can  not  be  produced  in  sufficient 
quantity  owing  to  the  fact  that  the  yeast  already  produced  has  exhausted 
the  yeast  food  in  the  wine.  Bacteria,  however,  are  able  to  increase,  and 
during  the  winter  often  spoil  the  wine.  It  is  a  great  mistake  to  trust  to 
the  spring  fermentation  to  complete  the  elimination  of  the  sugar.  While 
this  will  sometimes  occur  in  a  satisfactory  manner,  the  danger  of  the 
wine  spoiling  is  serious,  and,  in  any  case,  the  final  clearing  of  the  wine 
is  delayed  several  months. 

(c)  After  the  Fermentation.  As  soon  as  all  the',  sugar  has  been 
destroyed,  in  the  case  of  dry  wines,  or  the  desired  degree  of  attenuation 
has  been  obtained,  in  the  case  of  sweet  wines,  all  the  useful  work  of 
micro-organisms  has  been  accomplished.  The  quality  and  safety  of  the 
wine  then  depends  on  freeing  it  from  all  organisms  present  and  prevent- 
ing 1  he  en1  ranee  and  action  of  all  others. 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  435 

1.  Aging. — A  young  wine,  immediately  after  the  fermentation,  is 
cloudy.  Before  it  is  ready  for  consumption,  it  must  be  rendered  per- 
fectly and  permanently  clear.  This  is  accomplished  by  time  and  the 
various  operations  of  wine-handling.  A  perfectly  sound  and  dry  wine 
can  be  made  clear  by  filtration  and  other  means,  directly  after  the  fer- 
mentation is  over,  but  it  will  not  remain  clear.  Certain  salts  (cream 
of  tartar)  and  certain  albuminoid  matters  gradually  become  insoluble 
and  are  slowly  precipitated.  The  clear  wine  therefore  has  to  be  separ- 
ated from  these  insoluble  matters  repeatedly  until  they  practically 
cease  to  form  and  the  clearness  becomes  permanent. 

The  time  necessary  to  attain  this  condition  varies  with  the  kind  of 
wine,  the  temperature  and  the  amount  of  aeration.  Wines  rich  in 
extract  and  albuminoid  substances  clear  slowly  and  with  difficulty. 
The  difficulty  is  increased  if  the  wine  contains  a  small  remnant  of  sugar 
and  is  infected  with  many  disease  bacteria.  The  effect  of  the  temper- 
ature differs  according  to  the  kind  of  cloudiness.  The  lower  the 
temperature,  the  more  rapidly  yeasts  and  other  micro-organisms  become 
inactive  and  accumulate  in  the  sediment.  At  low  temperatures  the 
dissolving  power  of  the  wine  is  lessened  and  the  cream  of  tartar  tends 
to  go  out  of  the  solution  and  to  be  precipitated.  Many  of  the  albuminoid 
and  organic  substances,  on  the  other  hand,  are  eliminated  more  rapidly 
at  higher  temperatures.  A  wine  should,  therefore,  be  kept  as  cold  as 
practicable  for  several  weeks  after  the  fermentation  is  over.  This  will 
tend  to  throw  down  the  micro-organisms  and  salts.  After  separating 
from  the  sediment  thus  formed,  the  temperature  should  be  raised  for 
several  months  in  order  to  facilitate  certain  physical  and  chemical 
changes  which  result  in  rendering  other  matters  insoluble.  When 
separated  from  all  sediments,  the  wine  develops  best  at  an  even  temper- 
ature of  between  50°  and  60°  F. 

As  the  wine  clears,  it  also  undergoes  certain  favorable  changes  in  color, 
odor  and  taste  which  distinguish  an  old  from  a  young  wine.  These 
changes  are  due  partly  to  the  clearing  of  the  wine  and  partly  to  chem- 
ical combinations  and  reactions  between  the  various  constituents  of  the 
wine  under  the  influence  of  the  oxygen  of  the  air.  The  more  intense 
the  aeration  the  more  rapid  are  these  changes.  Small  casks  and  fre- 
quent rackings  increase  the  aeration  and,  therefore,  the  rapidity  of 
aging.  High  temperatures  have  the  same  effect.  Large  casks  and  low 
temperatures  retard  these  changes.  If  too  rapid,  the  wine  does  not 
acquire  its  finest  qualities  and  become  vapid;  if  too  slow,  the  aging  of 
the  wine  is  unduly  prolonged  and  the  wine  is  liable  for  a  longer  time 
to  the  possibility  of  injurious  changes. 

In  any  particular  case,  it  is  a  matter  of  judgment  how  rapidly  the 
aging  should  be  caused  to  progress.     In  a  general  way,  the  best  results 


436  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

in  quality  are  obtained  by  the  use  of  small  casks  and  low  temperatures. 
Where  low  temperatures  are  unavailable,  larger  casks  must  be  used. 

The  time  of  aging  is  determined  riot  only  by  the  attainment  of  stable 
limpidity  but  by  the  acquirement  of  the  odors  and  tastes  which  distin- 
guish a  properly  aged  wine.  Improvement  in  the  latter  respect  may 
continue  after  all  insoluble  matters  have  been  separated  from  the  wine. 
After  a  certain  time,  however,  every  wine  attains  its  optimum  quality. 
At  this  point  it  should  be  bottled  or  consumed  for  all  further  changes 
decrease  the  quality. 

The  point  of  optimum  quality  varies  greatly  with  the  character  of 
the  wine.  The  more  alcohol  and  extract  the  wine  contains  the  more 
slowly  it  acquires  its  highest  value.  Ports  and  sherries  may  improve 
for  twenty  or  thirty  years,  while  light  northern  wines  may  be  at  their 
best  in  one  or  two.  The  taste  of  the  consumer  must  also  be  taken  into 
account.  While  a  wine  in  aging  acquires  certain  qualities  such  as  the 
odors  grouped  as  " bouquet"  it  loses  certain  agreeable  aromas  preformed 
in  the  grape  and  which  are  most  marked  in  the  young  wine. 

2.  Backing. — As  soon  as  bubbles  of  C02  cease  to  be  given  off,  the  yeast 
and  other  solid  matters  will  settle  to  the  bottom  and  the  liquid  become 
clear.  This  often  occurs  before  the  fermentation  is  complete.  In  this 
case  the  temperature  should  be  kept  up  and  the  fermentation  stimulated 
by  .aeration  as  described  above. 

When  the  wine  is  dry  it  should  be  "racked"  (drawn  off,  decanted) 
from  the  sediment  into  clean  casks.  The  first  racking  is  usually  done 
while  the  wine  is  till  slightly  cloudy  during  the  first  month  or  six  weeks, 
to  remove  the  more  bulky  sediment.  If  left  too  long  in  contact  with 
the  yeast  the  autophagy  or  degeneration  of  the  latter  may  produce 
substances  which  injure  the  brightness  and  flavor  of  the  wine. 

A  second  racking  is  necessary  at  the  end  of  the  winter  before  the 
spring  rise  of  temperature  arrives  and  stimulates  the  vitality  of  the 
micro-organisms  which  always  remain  in  the  wine.  A  well-made  wine 
at  this  time  should  be  perfectly  bright  and  all  solid  matters  consisting 
of  yeast  and  bacteria,  coagulated  albuminoids  and  crystals  of  bitartrate 
should  have  accumulated  in  the  sediment. 

Racking  should  take  place  when  possible  only  in  settled  weather, 
when  the  barometric  pressure  is  high.  Low  atmospheric  pressures 
diminish  the  solubility  of  the  C02  with  which  the  wine  is  saturated. 
Under  these  conditions,  therefore,  bubbles  of  gas  are  apt  to  be  given 
off,  bringing  up  particles  of  sediment  and  rendering  the  wine  cloudy. 
However  long  wine  is  kept  in  wooden  casks,  it  will  continue  to  deposit 
traces  of  sediment,  owing  to  chemical  changes  due  to  the  action  of  ogygen 
which  penetrates  slowly  through  the  wood.  Repeated  rackings  are 
therefore  necessary,  occurring  at  least  twice  a  year  until  the  wine  is 
bottled  or  consumed. 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  437 

3.  Exclusion  of  Air. — Abundant  aeration  is  necessary  during  ferment- 
ation. A  moderate  supply  of  oxygen  is  necessary  for  the  proper  aging 
of  wine.  Experience  has  shown  that  exactly  the  proper  amount  of  pure 
filtered  air  will  obtain  access  to  the  wine  for  the  latter  purpose  through 
the  wood  of  ordinary  casks  of  proper  size. 

"With  sound,  completely  fermented  wines,  all  aeration  other  than 
that  due  to  the  porosity  of  the  wood  should  be  avoided  as  much  as  pos- 
sible. This  is  accomplished  by  keeping  the  casks  tightly  bunged  and 
completely  filled.  Evaporation  through  the  wood  continually  dimin- 
ishes the  volume  of  wine  and  the  lack  must  be  supplied  by  filling  up,  at 
first  two  or  three  times  a  month  and  later  every  month  or  two.  The 
drier  and  warmer  the  air  of  the  cellar,  the  more  frequent  the  fillings 
necessary. 

4.  Sulfuring. — A  light  sulfuring  of  the  clean  casks  into  which  the 
wine  is  racked  is  usual.  This  should  be  practised  with  great  caution. 
Very  little  is  needed  with  sound  wines,  especially  if  it  has  been  used 
before  or  during  fermentation  and  a  slight  excess  will  injure  the  flavor. 
The  amount  for  perfectly  dry  wines  should  not  exceed  .004  per  cent  for 
white  wine  and  less  for  red.  One  half  to  one  third  of  this  is  sufficient 
for  old  wines.  The  amount  can  be  accurately  measured  only  when 
using  meta-bisulfite  or  the  liquefied  gas,  and  is  equivalent  to  from  2  to  5 
ounces  of  meta-bisulfite  to  1,000  gallons  of  wine.  The  utility  of  the  S02, 
with  perfectly  sound  wines,  is  to  diminish  oxidation;  with  wines  liable 
to  disease,  to  discourage  the  growth  of  bacteria. 

5.  Cellar  Hygiene. — All .  manipulation  of  the  wines  should  be  con- 
ducted with  strict  attention  to  cleanliness.  Cleanliness  in  this  case 
means  not  only  absence  of  dirt,  but  the  prevention  of  the  development 
of  molds  and  bacteria.  The  alcohol,  acids  and  tannin  of  sound,  well- 
made  wines  have  certain  antiseptic  properties  which  prevent  injury  by 
the  small  infection  with  the  spores  which  exist  in  ordinarily  pure  air 
and  clean  water  and  which  it  is  impossible  to  avoid  entirely.  Any  wine, 
however,  may  be  injured  or  spoiled  by  the  abundant  infection  with 
harmful  micro-organisms  which  occurs  when  they  are  placed  in  contact 
with  dirty  hoses,  pumps  or  casks. 

All  the  surfaces  with  which  the  wine  comes  in  contact  should  be  thor- 
oughly cleaned  and  washed  immediately  after  use.  If  these  surfaces 
are  metallic  or  otherwise  non-absorbent,  they  should  be  kept  perfectly 
dry.  If  they  are  of  wood,  rubber  or  other  porous  material,  they  should 
be  preserved  from  bacterial  or  mold  growth  by  means  of  sulfurous  acid. 

Empty  casks  should  be  sulfured  by  burning  a  small  piece  of  sulfur 
in  each,  once  a  month,  for  three  or  four  months.  After  these  sulfurings 
the  casks  will  usually  be  perfectly  sterilized  and  the  sulfurings  need  then 
be  done  only  every  three  to  six  months.  Open  wooden  vats  may  be 
sulfured  in  the  same  way  if  they  can  be  covered  temporarily  with 


438  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

canvas  or  a  close  wooden  cover.  Spraying  or  swabbing  with  a  10  per 
cent  solution  of  calcium  sulfite  is  more  effective  if  the  vats  are  not 
covered.  Rubber  or  canvas  hoses  should  be  rinsed  with  a  sulfite  solu- 
tion and  hung  up  so  that  no  liquid  remains  in  them  and  washed  before 
using. 

Casks  or  vats  which  have  contained  spoiled  wine  or  been  permitted 
to  become  moldy  or  vinegar-sour  require  special  treatment  before  they 
are  used  again.  They  must  first  be  made  mechanically  clean  by  remov- 
ing all  sediment  with  scraper,  washing-chain  or  brush.  All  volatile  acid 
must  then  be  neutralized  by  treatment  with  a  hot  5  per  cent  to  10  per 
cent  solution  of  carbonate  of  soda.  Moldy  tastes  are  hard  to  remove. 
When  a  cask  becomes  badly  tainted  it  is  best  to  take  it  apart  and 
re-cooper  it  before  treatment.  When  less  badly  affected  and  when  all 
the  staves  are  sound,  the  moldy  taste  may  be  removed  by  treating  the 
dried  interior  with  hot  cotton-seed  oil.  After  the  oil  has  acted  for  two 
or  three  days,  it  should  be  removed  with  hot  water  and  soda. 

After  mechanical  cleaning  and  removal  of  all  bad  tastes,  the  cask 
should  be  sterilized.  Small  casks  are  most  easily  treated  with  boiling 
water  or  steam,  followed  by  heavy  sulfuring.  With  very  large  casks 
the  heads  and  staves  are  apt  to  be  warped  by  this  treatment.  In  this 
case,  several  heavy  sulfurings  at  intervals  of  several  days  are  effective. 

6.  Clarification. — The  clarification  of  a  perfectly  sound  wine  may  be 
facilitated  and  hastened  by  thoroughly  stirring  up  the  yeast  imme- 
diately before  the  first  racking.  The  yeast  in  settling  carries  down 
much  of  the  finer  suspended  matter,  thus  effecting  a  rough  fining. 
Materials  such  as  kaolin,  pure  silica  sand,  charcoal  and  filter  paper 
can  be  used  with  the  same  effect  after  the  first  racking.  The  fining, 
however,  is  never  perfect  and  the  flavor  of  the  wine  is  often  injured  by 
the  materials  used.  A  very  pure  clay,  known  commercially  as  Spanish 
clay,  is  used  largely  for  clearing  sweet  wines  where  the  flavor  is  not  so 
delicate.     From  .5  to  1  pound  per  100  gallons  is  used  for  this  purpose. 

The  best  wines  are  nearly  always  fined  at  least  once  immediately 
before  bottling.  One  or  two  finings  may  precede  this  to  hasten  aging, 
defecation  and  bottle  ripeness. 

The  materials  used  are  soluble  gelatinous  or  albuminous  substances 
which  are  capable  of  being  coagulated  and  precipitated  by  some  ingre- 
dient of  the  wine.  The  best  of  the  commonly  used  substances  are 
Isinglas  (Ichthyocol)  \  to  \  an  ounce  per  100  gallons  for  white  wines; 
1  he  white  of  fresh  eggs,  4  to  8  per  100  gallons  for  red,  and  gelatin  1  to  1J 
ounces  per  100  gallons  for  either.  The  amount  used  depends  on  the 
degree  of  cloudiness. 

The  proper  quantity  of  the  finings  is  first  dissolved  in  a  little  water, 
then  diluted  with  wine  and  stirred  into  the  cask.  The  tannins  and  acids 
of  the  wine  cause  a  gradual  coagulation  in  minute  particles  throughout 


Bulletin  213]  THE  PRINCIPLES  OF  WINE-MAKING.  439 

the  liquid.  These  particles  gradually  coalesce,  forming  larger  particles 
which  include  all  the  other  floating  solid  matter  of  the  wine  as  in  a  net. 
These  larger  particles,  contracted  by  the  alcohol,  then  settle  to  the  bot- 
tom, leaving  the  wine  perfectly  bright. 

The  coagulum  consists  of  a  combination  of  the  gelatinous  matter  and 
the  tannin.  Some  of  the  latter,  therefore,  is  removed  from  the  wine. 
With  astringent  red  wines,  this  may  be  an  improvement.  If  there  is  no 
excess  of  tannin  present,  enough  must  be  added  to  combine  with  the 
finings  used.  With  white  wines,  which  contain  little  or  no  tannin,  this 
addition  is  always  necessary. 

The  amount  to  use  varies  with  the  quality  of  the  finings  and  of  the 
tannin  and  with  the  composition  and  temperature  of  the  wine. 

To  precipitate  commercial  gelatin  of  good  quality  about  an  equal 
quantity  of  good  tannin  is  necessary;  isinglass  properly  prepared 
requires  only  from  one  half  to  one  third  this  amount.  Eggs  require 
only  minute  quantities. 

Specially  prepared  casein  of  milk  is  also  used  for  fining  white  wine. 
Its  chief  merit  is  that  the  acids  of  the  wine  alone  cause  its  complete  pre- 
cipitation and  no  addition  of  tannin  is  needed.  Many  other  albuminous 
substances  such  as  milk,  blood  and  various  proprietary  preparations  are 
also  used,  but  they  are  all  inferior  to  the  three  mentioned  and  many  of 
them  introduce  foreign  matters  such  as  milk-sugar  and  bacteria,  which 
are  a  source  of  danger  to  the  wine. 

Wines  containing  many  disease  bacteria  may  be  injured  by  the  intro- 
duction of  finings.  The  evolution  of  gases  due  to  the  bacterial  action 
may  prevent  the  settling  and  the  albuminoid  matters  introduced  will 
favor  the  multiplication  of  the  disease  organisms.  By  means  of  a  light 
sulfuring  or  the  addition  of  about  .5  oz.  to  1  oz.  meta-bisulfite  to  a  100 
gallons  added  immediately  before  the  addition  of  the  gelatin,  the  bacteria 
may  be  temporarily  paralyzed  and  the  finings  will  then  settle  and  remove 
the  bacteria  with  the  other  floating  particles. 

The  bright  wine  should  be  racked  from  the  finings  very  soon  after 
the  sediment  has  settled,  especially  when  the  disease  bacteria  are  numer- 
ous. This  will  be  in  from  seven  to  ten  or  at  most  twenty  days.  If  the 
wine  is  not  clear  in  three  weeks  it  should  be  filtered. 

7.  Filtration. — Filtering  is  inferior  to  fining  in  producing  a  perfectly 
bright  wine.  It  is  more  rapid,  however,  and  is  useful  in  clearing  com- 
mon wine  and  wines  refractory  to  finings.  Filters  of  innumerable 
forms  are  used.  They  are  of  two  main  types.  For  rough  clearing  of 
very  cloudy  wines  some  form  of  bag  filter  is  usually  employed  in  which 
the  wine  passes  through  a  cloth  tissue.  The  passage  at  first  is  rapid 
and  the  filtration  imperfect.  As  the  solid  matter  accumulates  on  the 
filtering  surf ace?  the  filtration  improves  but  the  passage  of  the  wine  is 

4— b213 


4-iO  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION. 

retarded.  The  first  wine  is  passed  a  second  time  through  the  filter  and 
as  soon  as  the  rate  of  filtration  becomes  too  slow,  the  operation  must  be 
stopped  and  the  filtering  surface  renewed. 

For  wines  containing  little  sediment,  the  filter  must  be  primed.  This 
is  accomplished  by  putting  a  little  finings  in  the  wine  first  passed 
through  the  filter.  The  priming  is  more  effective  and  the  output  of  the 
filter  much  increased  if  a  little  infusorial  earth  free  from  iron  and  car- 
bonates is  used  with  the  gelatin. 

For  the  more  perfect  clearing  of  old  wines  some  form  of  pulp  filter  is 
used.  These  are  various  devices  by  which  the  wine  is  forced  through 
a  mass  of  cellulose  or  asbestos  pulp  and  freed  from  all  floating  matter. 
Some  of  the  best  of  these,  carefully  used,  remove  nearly  all  the  bacteria 
present. 

8.  Heating. — The  heating  of  wine  after  fermentation  is  practised  for 
various  purposes  and  in  various  ways.  In  general  its  object  is  to  hasten 
and  facilitate  the  chemical  and  physical  changes  which  constitute  aging, 
to  sterilize  the  wine  completely  or  partially  (pasteurization)  by  the 
destruction  of  micro-organisms  or  for  both  purposes  at  the  same  time. 

Wines  will  develop  more  rapidly  at  high  temperatures  than  at  low. 
The  aging  of  a  wine  can  often  be  much  hastened  with  advantage  by  keep- 
ing it  in  a  warm  room,  70°  to  75°  F.,  for  several  weeks  or  even  months. 
This  must  be  done,  however,  with  much  caution.  Only  young  wines 
which  are  perfectly  dry  and  clear  should  be  subjected  to  this  treatment. 
Wines  containing  unfermented  sugar  or  many  bacteria  are  almost 
certain  to  become  diseased  if  kept  in  a  warm  place  after  they  have 
ceased  alcoholic  fermentation.  Wines  low  in  alcohol  or  of  delicate  con- 
stitution in  any  way  may  be  injured.  In  any  case,  the  wine  will  age 
too  much,  become  vapid  or  acquire  a  sherry  taste  if  kept  warm  too  long. 

The  precipitation  of  albuminoid  matters  is  much  facilitated  by  this 
heating  which  is  used  by  some  wine-makers  in  the  finishing  of  Sauternes 
containing  1  or  2  per  cent  of  sugar.  In  this  case,  the  young,  clear  wine 
is  placed  for  several  days  or  weeks  in  a  room  or  cellar  heated  to  85°  to 
90°  F.  Under  these  conditions,  the  wine  is  extremely  subject  to  bac- 
terial deterioration.  This  is  prevented  either  by  the  use  of  compar- 
atively large  doses  of  sulfurous  acid  or  by  a  momentary  heating  to 
150°  F.  to  sterilize  the  wine  before  the  prolonged  heating  at  90°  F. 
Some  sulfurous  acid  is  necessary  in  order  to  prevent  browning  and  dark- 
ening of  the  color  and  the  acquiring  of  a  sherry  taste.  A  still  higher 
heating  is  used  for  certain  sweet  wines  to  which  it  is  desired  to  give  a 
"rancio"  or  sherry  taste.  In  this  case,  the  wine  is  heated  to  120°  or 
130  F.  for  two  or  three  months.  This  high  and  prolonged  heating 
promotes  the  chemical  changes  which  produce  the  "rancio"  taste  and 
golden  color  due  to  oxidation  and  caramelizes  part  of  the  sugar,  giving 
;i  desired  character  to  the  sweet  wine. 


Bulletin  213]  the  principles  OF   wine-making.  441 

9.  Pasteurization. — The  pasteurization  of  wine  has  for  its  object  the 
destruction  of  all  injurious  micro-organisms  in  the  liquid.  It  is  accom- 
plished by  a  momentary  heating  to  a  temperature  of  between  140°  F. 
and  160°  F.;  or  sometimes  higher. 

As  the  wine  is  cooled  immediately  and  remains  at  the  maximum 
temperature  for  only  one  minute  or  less,  the  changes  of  composition  and 
character  are  much  less  marked  than  in  the  case  of  prolonged  heating. 
Such  changes,  however,  do  occur  and  the  more  intensely  the  higher  the 
temperature  of  pasteurization.  Sound  wines  are  sometimes  pasteur- 
ized to  insure  their  keeping  under  unfavorable  conditions.  They  may  be 
pasteurized  into  casks  for  shipping  long  distances  or  in  hot  climates. 
Delicate  wines  are  sometimes  pasteurized  in  bottles. 

Pasteurization  is  also  a  useful  means  of  checking  the  progress  of 
bacterial  diseases  of  wine  before  they  have  injured  its  quality  irretriev- 
ably. When  an  early  microscopic  examination  of  the  wine  shows  the 
presence  of  dangerous  numbers  of  bacteria,  prompt  pasteurization  will 
destroy  them  before  they  have  perceptibly  injured  the  wine.  Pasteur- 
ization, however,  does  not  render  the  wine  immune,  and  the  sterilized 
wine  must  be  run  into  sterilized  casks  and  protected  from  reinfection. 
The  need  of  pasteurization  is  proof  of  the  delicate  constitution  of  the 
wine  and  of  the  need  of  special  care  even  after  the  destruction  of  the 
bacteria  it  contains. 

Wines  of  any  age  may  be  pasteurized  but  they  should  always  be 
nearly  or  quite  clear.  Heating  cloudy  wine  always  injures  its  flavor 
and  often  makes  it  more  difficult  to  clarify.  Before  heating  a  cloudy 
wine,  therefore,  it  should  be  cleared  by  fining  or  filtration. 

10.  Cooling. — Low  temperatures  may  be  utilized  to  promote  the  devel- 
opment of  wine.  As  soon  as  the  wine  is  completely  dry,  which  should  be 
within  a  few  weeks  after  the  end  of  the  vintage,  it  is  benefited  by  being 
cooled.  Low  temperatures,  by  diminishing  the  activity  of  the  micro- 
organisms, tend  to  cause  them  to  accumulate  in  the  sediment  with  the 
cream  of  tartar,  and  to  increase  the  limpidity  of  the  wine  at  the  first 
racking. 

The  cold  of  winter  arriving  at  just  about  the  right  time  for  this 
purpose,  should  be  utilized  by  opening  the  cellar  where  the  young  wine 
is  stored  at  night  and  closing  it  in  the  day  time.  In  some  countries, 
the  wine  is  placed  outside  during  part  of  the  first  winter  in  order  to 
obtain  the  full  benefit  of  the  chilling.  Lately  artificial  cooling  to  35°  or 
40°  F.  has  been  used  with  success.  The  wine  should  be  left  at  these 
low  temperatures  only  so  long  as  is  necessary  to  cause  all  micro-organ- 
isms and  excess  of  salts  to  accumulate  in  the  sediment  and  to  be  removed 
by  the  first  racking.  A  rise  of  temperature  to  55°  to  65°  F.  is  then 
desirable  for  the  maturing  of  the  wine. 


442  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

11.  Bottling  Wine. — The  object  of  bottling  is  to  preserve  the  wine  as 
much  as  possible  from  further  change  by  protecting  it  from  the  action 
of  micro-organisms  and  oxygen. 

A  wine,  therefore,  which  has  ceased  forming  a  deposit,  is  perfectly 
bright  and  has  reached  its  optimum  quality  should  be  bottled.  It  is 
usually  advisable  to  fine  a  wine  two  to  five  weeks  before  bottling.  It 
may  be  bottled  directly  from  the  finings  or,  preferably,  racked  carefully 
from  them  as  soon  as  bright  into  lightly  sulfured  casks  and  bottled 
after  two  or  three  weeks  rest. 

If  bottled  too  young,  the  wine  will  make  an  abundant  deposit  in  the 
bottle,  if  too  old,  it  will  have  lost  something  of  its  quality.  If  bottled 
at  the  right  stage  and  in  perfect  condition,  there  will  be  very  little 
deposit  and  this  will  be  slow  in  forming  and  will  adhere  firmly  to  the 
side  of  the  bottle.  The  age  of  the  wine  will  vary  in  California  in 
ordinary  cases,  from  one  and  a  half  years  to  four  or  five  years.  It  is 
seldom  desirable  to  keep  even  the  heaviest  dry  wines  in  casks  longer 
than  five  years  and  it  is  possible  by  special  methods  to  get  some  light 
wines  ready  for  bottling  in  less  than  a  year. 

The  bottling  should  take  place  under  the  same  atmospheric  conditions 
as  racking,  in  order  to  have  the  sediment  as  compact  as  possible  and  the 
wine  as  free  as  possible  from  floating  particles  or  micro-organisms.  The 
placing  of  the  cask  and  the  drawing  of  the  wine  into  bottles  should  be 
so  arranged  that  the  wine  is  disturbed  as  little  as  possible  during  the 
operation. 

Bottles  and  casks  should  be  perfectly  clean  and  sterile.  The  former 
should  be  washed  in  hot  water  containing  ten  per  cent  of  carbonate  of 
soda,  rinsed  with  pure  water  and  allowed  to  dry  neck  down.  A  final 
rinsing,  before  draining,  with  brandy  or  a  weak  solution  of  meta-bisulfite 
is  of  use  in  some  cases,  but  should  be  done  with  precautions  to  prevent 
more  than  a  trace  of  the  rinsing  solution  from  remaining  in  the  bottle 
when  filled  with  wine.  The  corks  should  be  soaked  for  twenty-four 
hours  in  warm  water  and  then  drained  and  rinsed  with  the  wine  to  be 
bottled.  Old  or  inferior  corks  should  be  sterilized  by  immersing  for 
twenty-four  hours  in  a  5  to  10  per  cent  solution  of  sulfuric  acid  before 
washing  and  soaking.  They  may  be  sterilized  more  effectively  and 
easily  by  heating  them  in  a  closed  vessel  in  which  is  placed  a  small 
amount  of  a  20  per  cent  solution  of  formalin.  Eight  or  ten  ounces 
of  formalin  in  one  quart  of  water  is  sufficient  to  treat  1,000  corks. 

After  bottling,-  the  wine  is  further  protected  from  access  of  air  by 
covering  the  corks  with  a  layer  of  hot  paraffin  or  wax.  The  bottles 
should  then  be  laid  horizontally,  care  being  taken  that  the  small  volume 
of  air  which  remains  in  the  bottle  is  not  in  contact  with  the  cork  but  in 
contact  with  the  glass  of  the  upper  side  of  the  bottle. 

Wine  bottled  in  this  way  will  improve  a  little  for  a  few  months  and 
then  remain  with  little  change  for  many  years  if  kept  in  a  cool,  moder- 
ately  moist  and  clean  cellar. 


STATION     PUBLICATIONS    AVAILABLE     FOR     DISTRIBUTION. 


REPORTS. 


1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  regard- 

ing the  Vintages  of  1894-95. 

1897.  Resistant  Vines,  their  Selection,  Adaptation,  and  Grafting.     Appendix  to  Viti- 

cultural Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-03. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-04. 


BULLETINS. 


Reprint.    Endurance  of  Drought  in  Soils  of 

the  Arid  Region. 
No.  128.  Nature,  Value,  and  Utilization  of 
Alkali  Lands,  and  Tolerance  of 
Alkali.      (Revised  and  Reprint, 
1905.) 

133.  Tolerance    of   Alkali   by  Various 
cultures. 

147.  Culture  Work  of  the  Sub-stations. 

149.  California  Sugar  Industry. 

151.  Arsenical  Insecticides. 

153.  Spraying  with  Distillates.' 

159.  Contribution  to  the  Study  of  Fer- 
mentation. 

162.  Commercial  Fertilizers.     (Dec.  1, 
1904.) 

165.  Asparagus    and   Asparagus   Rust 
in   California. 

167.  Manufacture    of    Dry    Wines    in 

Hot  Countries. 

168.  Observations  on  Some  Vine  Dis- 

eases in  Sonoma  County. 

169.  Tolerance  of  the  Sugar  Beet  for 

Alkali. 

170.  Studies  in  Grasshopper  Control. 

171.  Commercial       Fertilizers.      (June 

30,  1905.) 

172.  Further  Experience  in  Asparagus 

Rust  Control. 
174.  A  New  Wine-cooling  Machine. 

176.  Sugar  Beets  in  the  San  Joaquin 

Valley. 

177.  A   New   Method   of   Making  Dry 

Red  Wine. 

178.  Mosquito  Control. 

179.  Commercial    Fertilizers.       (June, 

1906.) 

180.  Resistant  Vineyards. 

181.  The  Selection  of  Seed- Wheat. 

182.  Analysis  of  Paris  Green  and  Lead 

Arsenic.      Proposed  Insecticide 
Law. 

183.  The  California  Tussock-moth. 

184.  Report  of  the  Plant  Pathologist 

to  July  1,  1906. 

185.  Report     of     Progress     in     Cereal 

Investigations. 


No.   186. 
187. 

188. 

189. 

190. 
191. 
192. 

193. 


194. 


195. 
197. 


198. 
199. 
200. 

201. 

202. 

203. 

204. 

205. 

206. 

207. 
208. 
209. 
210. 

211. 

212. 


The  Oidium  of  the  Vine. 

Commercial  Fertilizers.  (Jan- 
uary,  1907.) 

Lining  of  Ditches  and  Reservoirs 
to  Prevent  Seepage  and  Losses. 

Commercial  Fertilizers.  (June, 
1907.) 

The  Brown  Rot  of  the  Lemon. 

California  Peach  Blight. 

Insects  Injurious  to  the  Vine  in 
California. 

The  Best  Wine  Grapes  for  Cali- 
fornia ;  Pruning  Young  Vines ; 
Pruning  the  Sultanina. 

Commercial  Fertilizers.  (Dec, 
1907.) 

The  California  Grape  Root-worm. 

Grape  Culture  in  California ; 
Improved  Methods  of  Wine- 
making  ;  Yeast  from  California 
Grapes. 

The  Grape  Leaf-Hopper. 

Bovine  Tuberculosis. 

Gum  Diseases  of  Citrus  Trees  in 
California. 

Commercial  Fertilizers.  (June, 
1908.) 

Commercial  Fertilizers.  (Decem- 
ber, 1908.) 

Report  of  the  Plant  Pathologist 
to  July  1,  1909. 

The  Dairy  Cow's  Record  and  the 
Stable. 

Commercial  Fertilizers.  (Decem- 
ber,   1909.) 

Commercial  Fertilizers.  (June, 
1910.) 

The  Control  of  the  Argentine  Ant. 

The  Late  Blight  of  Celery. 

The  Cream  Supply. 

Imperial  Valley  Settlers'  Crop 
Manual. 

How  to  Increase  the  Yield  of 
Wheat  in  California. 

California  White  Wheats. 


CIRCULARS. 


No.     1.  Texas  Fever. 

5.  Contagious  Abortion  in  Cows. 
7.  Remedies  for  Insects. 
9.  Asparagus  Rust. 

11.  Fumigation  Practice. 

12.  Silk  Culture. 

15.  Recent    Problems    in    Agriculture. 
What  a  University  Farm  is  For. 
19.  Disinfection  of  Stables. 

29.  Preliminary    Announcement    Con- 

cerning Instruction  in  Practical 
Agriculture  upon  the  University 
Farm,  Davisville,  Cal. 

30.  White  Fly  in  California. 

32.  White   Fly  Eradication. 

33.  Packing    Prunes    in    Cans.      Cane 

Sugar  vs.  Beet  Sugar. 

36.  Analysis  of  Fertilizers  for  Con- 
sumers. 

39.  Instruction  in  Practical  Agricul- 
ture at  the  University  Farm. 


No.   46.   Suggestions  for   Garden   Work   in 
California  Schools. 

47.  Agriculture  in  the  High  Schools. 

48.  Butter  Scoring  Contest,   1909. 

50.  Fumigating   Scheduling. 

51.  University  Farm  School. 

53.  Announcement  of  Farmers'   Short 

Courses  for  1910. 

54.  Some     Creamery     Problems     and 

Tests. 

55.  Farmers'  Institutes  and  University 

Extension  in  Agriculture. 

58.  Experiments  with  Plants  and  Soils 

in     Laboratory,     Garden,     and 
Field. 

59.  Tree      Growing      in      the      Public 

Schools. 

60.  Butter  Scoring  Contest,  1910. 

61.  University  Farm  School. 

62.  The  School  Garden  in  the  Course' 

of  Study. 


